Gears

I disagree @twangster. I believe you're inferring what the CDC believes, and until they specify an issue with B2B, there is no reason to believe they look at consecutive cruises as anything more than two cruises in a row.
The CSO goes into great detail about what cruises line can and cannot do. They would certainly specify if there was an issue with B2B.
All that being said, CDC has no idea a B2B is a thing in cruising.  They constantly refer to cruises in terms of days instead of nights. 
Not saying they may not amend things as they go on, but they're not going to leave something as important as not permitting passengers on multiple cruises and putting permission to cruise in jeopardy(as you suggest) without actually stating that.  

Someone at the CDC is right now at this moment saying this to a coworker... "I told you so, now pay up".
 

In line with what @Gears mentioned, another strange occurrence is seeing your cruise ship Captain riding a Harley around Labadee.  
Captain Johnny keeps his personal Harley on board the ship.  
I was on this sailing when he tweeted this.  Saw him riding it around.
 
 
 
 

Perhaps not well known that you can do this (at least you could at one time...back in 2009)...
Embarkation day at Port Everglades for a 7 night Eastern Caribbean itinerary...about 12 motorcycles were loaded on to the ship. A group had arranged to have them on the ship and go on self guided tours at some of the ports of call.
Port day at St. Thomas...about 4:00 pm...beep beep beep...of the tow truck backing up with a bent up Harley Davidson Buell hanging on the hook. Watching them get it loaded back into the cargo hold...that was interesting.
Rider was OK...some scrapes, bruises and a damaged ego, but was lucky.

Perhaps not well known that you can do this (at least you could at one time...back in 2009)...
Embarkation day at Port Everglades for a 7 night Eastern Caribbean itinerary...about 12 motorcycles were loaded on to the ship. A group had arranged to have them on the ship and go on self guided tours at some of the ports of call.
Port day at St. Thomas...about 4:00 pm...beep beep beep...of the tow truck backing up with a bent up Harley Davidson Buell hanging on the hook. Watching them get it loaded back into the cargo hold...that was interesting.
Rider was OK...some scrapes, bruises and a damaged ego, but was lucky.

Perhaps not well known that you can do this (at least you could at one time...back in 2009)...
Embarkation day at Port Everglades for a 7 night Eastern Caribbean itinerary...about 12 motorcycles were loaded on to the ship. A group had arranged to have them on the ship and go on self guided tours at some of the ports of call.
Port day at St. Thomas...about 4:00 pm...beep beep beep...of the tow truck backing up with a bent up Harley Davidson Buell hanging on the hook. Watching them get it loaded back into the cargo hold...that was interesting.
Rider was OK...some scrapes, bruises and a damaged ego, but was lucky.

Perhaps not well known that you can do this (at least you could at one time...back in 2009)...
Embarkation day at Port Everglades for a 7 night Eastern Caribbean itinerary...about 12 motorcycles were loaded on to the ship. A group had arranged to have them on the ship and go on self guided tours at some of the ports of call.
Port day at St. Thomas...about 4:00 pm...beep beep beep...of the tow truck backing up with a bent up Harley Davidson Buell hanging on the hook. Watching them get it loaded back into the cargo hold...that was interesting.
Rider was OK...some scrapes, bruises and a damaged ego, but was lucky.

Perhaps not well known that you can do this (at least you could at one time...back in 2009)...
Embarkation day at Port Everglades for a 7 night Eastern Caribbean itinerary...about 12 motorcycles were loaded on to the ship. A group had arranged to have them on the ship and go on self guided tours at some of the ports of call.
Port day at St. Thomas...about 4:00 pm...beep beep beep...of the tow truck backing up with a bent up Harley Davidson Buell hanging on the hook. Watching them get it loaded back into the cargo hold...that was interesting.
Rider was OK...some scrapes, bruises and a damaged ego, but was lucky.

I see the RCL stock price is down about 2% on news of your cancellations... ?

I echo that.
On Monday I was generally positive. Today (Friday), that positivity has disappeared and has been replaced with the opposite.
The deal breakers, all the black Friday, extended to the weekend and then cyber Monday deals...only to outright cancel the cruises a day or two later they were advertising sales for. The continual marketing to buy-buy-buy only to announce more cancelations and say 'we don't know when' followed by more buy-buy-buy marketing...not a place I want to keep our money waiting.
We'll look at coming back when there are green lights across the board.

I see the RCL stock price is down about 2% on news of your cancellations... ?

I see the RCL stock price is down about 2% on news of your cancellations... ?

I echo that.
On Monday I was generally positive. Today (Friday), that positivity has disappeared and has been replaced with the opposite.
The deal breakers, all the black Friday, extended to the weekend and then cyber Monday deals...only to outright cancel the cruises a day or two later they were advertising sales for. The continual marketing to buy-buy-buy only to announce more cancelations and say 'we don't know when' followed by more buy-buy-buy marketing...not a place I want to keep our money waiting.
We'll look at coming back when there are green lights across the board.

I see the RCL stock price is down about 2% on news of your cancellations... ?

In fairness to Royal I don't know that any other cruise line is any better right now.  They all seem to be having money problems and can't pay out refunds that are due.  That's inevitable with no revenue for a year.
I'm hesitant to give money to any vacation company that requires 100% payment 3 months in advance right now.  The risk-reward isn't there.  If the cruise lines fail I don't want to be the one out of pocket for thousands of dollars. 
Hotels you can pay when you get there.    I can deal with that in 2021 once travel becomes a reality.  

I see the RCL stock price is down about 2% on news of your cancellations... ?

I echo that.
On Monday I was generally positive. Today (Friday), that positivity has disappeared and has been replaced with the opposite.
The deal breakers, all the black Friday, extended to the weekend and then cyber Monday deals...only to outright cancel the cruises a day or two later they were advertising sales for. The continual marketing to buy-buy-buy only to announce more cancelations and say 'we don't know when' followed by more buy-buy-buy marketing...not a place I want to keep our money waiting.
We'll look at coming back when there are green lights across the board.

I see the RCL stock price is down about 2% on news of your cancellations... ?

I see the RCL stock price is down about 2% on news of your cancellations... ?

I see the RCL stock price is down about 2% on news of your cancellations... ?

I echo that.
On Monday I was generally positive. Today (Friday), that positivity has disappeared and has been replaced with the opposite.
The deal breakers, all the black Friday, extended to the weekend and then cyber Monday deals...only to outright cancel the cruises a day or two later they were advertising sales for. The continual marketing to buy-buy-buy only to announce more cancelations and say 'we don't know when' followed by more buy-buy-buy marketing...not a place I want to keep our money waiting.
We'll look at coming back when there are green lights across the board.

You're not the only one. ?
They will have plan B, C, etc. They're just talking about all the options behind their closed doors and not telling us ? what they are looking at. RCI hasn't announced cancellations to the degree other cruise lines have...could be a very good reason behind that. ?

Refunds of cruises is variable for me. 
In cases where I have a refundable deposit before final payment and I choose to cancel I have been getting refunds in 7 to 21 days.
Refunds of cruise planner purchases are back to pre-pandemic timeframes.
I had over 20 cruises booked with them going into this pandemic.   There have been enough WTF moments dealing with various cancellations that it has soured my opinion of the cruise line.  Around 75% of those 20 bookings cancelled gracefully.  I'm down to 4 cruises booked that are non-refundable and I'm hoping they eventually cancel so I go through the refund process as painful as that may be.   
Where I struggle with refunds is when Royal introduces shenanigans when cruises are cancelled.  I've had a couple of cruises where Royal is playing games.  In separate cases they have covertly changed refundable bookings to non-refundable and you only have 24 hours to catch when they do this or they refuse to switch it back.  Then the cruise is cancelled and they only allow FCC or change the options since it was not a refundable booking (which it was).
For two other cases where they cancelled the cruise and we requested the refund option they ignored that and proceed differently. 
One was issued as FCC despite requesting a refund.  Eventually this was resolved and a refund was issued 78 days later.
The other is pending resolution.  This time they chartered the ship for a 2022 cruise and they gave us three options.  The option for price protection was to a date that had no cabin availability for what we had originally booked.  How they thought this was equitable or doable remains a mystery.  We chose the refund option.  Following up several weeks later they claimed we were not eligible for a refund since we cancelled the cruise.  They chartered the ship and they cancelled the cruise.  After escalating they have stated they will refund our deposit in 45 days.  Time will tell.    
To be completely honest I've lost faith in Royal Caribbean.  I've cruised them a fair bit and up to this point they would always do the right thing when things went wrong due from everything like hurricanes or a crane fell on a ship. 
I get the company is struggling and navigating uncharted waters but that doesn't give them license to lie, cheat and steal.  All I want is honesty and fairness even if it takes months to do the right thing, the thing they say they will do but then they proceed in a different direction making false claims and refusing refunds that are clearly due.  
My personal approach right now is to book nothing more with Royal until the pandemic is clearly over and everything is back to normal.  Once bitten twice shy sort of thing.  
I like Royal in general but they've lost their way in this pandemic.  Once I see them getting back to the Royal I used to know I'll come back.

You're not the only one. ?
They will have plan B, C, etc. They're just talking about all the options behind their closed doors and not telling us ? what they are looking at. RCI hasn't announced cancellations to the degree other cruise lines have...could be a very good reason behind that. ?