While it’s still very unlikely, I don’t think a revival of something BttF in the parks is truly out the window.
I definitely think Universal is slowly realizing how powerful nostalgia is, and even though this is really only showing through their merch offerings right now I don’t think a new attraction based of any “retro” property could be far off. I would be shocked if Jaws, BttF, and E.T. merch weren’t outselling F&F, Bourne, MIB, Mummy, Fallon, and Rockit stuff.
Eventually Universal is going to wear themselves thin only using “current” properties across 3 theme parks, and they’re already constructing a land based on a 100+ year old franchise in their newest park. I’d find it hard to believe at least one person at Creative hasn’t at least thought of a BttF concept replacing Simpsons if the contract really is coming to a close in 2028.