If MMRR is the attraction we think it is than I believe it preserves Toontown for at least 2 decades.I really don't see it. Why reduce area in Toontown right after you open a major attraction? And where do you move Mickey and Minnie M&G? I think the addition of MMRR preserves Toontown for more than a decade. I believe they will do away with subs/autopia and redevelop Tomorrowland before they even think of losing the West side of TT. Not to mention a third GE attraction behind Smuggler's where the Parade building is now.
So being that Galaxies Edge has a simulator and the dark ride of dark rides that must mean that the third attraction has to be an indoor roller coaster.