Yeah, but Twisters as a standalone might not last in the long run, as it is unlikely to have a franchise in the future, so having Twisters as part of the Studio Tour will at least raise more interest among the guests. You're right about the Studio Tour needing a little more “variety”, but the Earthquake acts like a normal earthquake attraction (with no mentioning of the 1974 film at all), whereas Twisters would be more aligned with the defunct Twister ride at USF, similar to the current King Kong 3D ride within the Studio Tour.
As for BTTF, I don't think it will come back again, but I would love to see it as part of the nighttime tour in the Courthouse Square, like the Minecraft version of Universal Studios released last year. The collapsing bridge should also be brought back to replace King Kong 3D as well, but I doubt it unfortunately.