Not sure how many here follow @monorailmedic's blog Cruise Habit, but he recently put up a post discussing a fleet-wide refurbishment for Celebrity that will start in 2019 and is planned to wrap up by 2023. This sounded pretty impressive to me, especially as they indicated that on at least some ships they were going to not just refresh the decor of the cabins, but totally tear out a bunch and replace them with new designs and architecture. Plus changes to common spaces, a new sundeck and lounge, and more!
The timing is really interesting for me, as I'm looking at a 2020 booking and was seriously considering a few itineraries on the Eclipse. If that ship has its refurbishment towards the start of the cycle, I could have an even nicer experience than I was already looking at!