COP is kind of an obvious one because of the ending, but I'm less concerned about the content and more concerned about fixing maintenance issues in that attraction.
Embarrassing carpet, awful seats, subpar audio, and animatronic John needing a lot of TLC. I wish they'd just completely gut that theater and give it the attention it deserves. I think of the ending as a little "classic" future vision. It sort of doesn't need an updated ending with hover cars and teleportation to be done well. "Car Phone" and a few minor things could be changed, but the spirit of progress is really what the shows is conveying.
With that rant over, I'd still say there are rides ahead of that in need of TLC. Not a change of concept, but just a good cleaning, maintenance concerns addressed, updated audio, perhaps a few tweaks to script or show scenes, etc.
These are just a few I view ahead of COP, although that's in dire need as well.
1) Practically anything at EPCOT
2) Great Movie Ride
3) Buzz Lightyear (Disneyland's is much better executed)
4) Backlot Tour
5) Bug's Life
6) Philhar Magic
I could go on. There is so much needing TLC/refurbishment but we aren't going to get it until they figure out Magic Bands.