Retheming Marvel Superhero Island into something else is a big no. Universal does not want to give up the theme park rights to Marvel. That contract doesn't allow Disney to use Marvel IPS that Universal is using east of the Mississippi River. That means Disney can't use The Avengers, X-Men, Spider-Man, and Fantastic Four for WDW.
Universal is looking at there is too much money making off money for Universal to give up those rights.
Also be happy that Universal has the rights to Marvel in Orlando based on Disney is using the IP for Avengers Campus in Walt Disney Studios Park. People have said that Spider-man ride at Universal is way better than what Disney has for Avengers Campus. People also have said that about the Spider-man ride at DCA and at at Walt Disney Studios Park.
Avengers Assemble: Flight Force replaced Rock'n Roller Coaster at Walt Disney Studios Park, but the ride by a lot of people is worse than Rock'n Roller Coaster despite using the same tracks. Bob Chapek and Josh D’Amaro are not happy with the finish product of Avengers Assemble: Flight Force and there are rumors that the attraction will be down for refurbishment in early 2023. Here are 2 websites with the rumor: https:///2022/08/disney-ride-closing-rumor-ld1/
https://airmagique.net/2022/07/25/rumor-disneyland-paris-to-close-new-avengers-flight-force-roller-coaster-for-plussing-refurbishment/#:~:text=While no refurbishment date has,blame on an insufficient budget.
What happened there was People who worked the reimagineering of Rock'n Roller Coaster to Avengers Assemble: Flight Force complained that the current state of the ride is due to their lack of budget. That means Disney Management screwed up the ride and they are forced to do something about it.
What I mentioned about Avengers Assemble: Flight Force quality could've easily happened at WDW if it wasn't for that contract. Be happy Disney got Cosmic rewind instead of Chapek wanting retheme DHS rides Avenger themed rides or make Tomorrowland into a Marvel Land.