For those that are curious...
Not 100% accurate, but accurate enough to give an idea of how much is available back there. South of RnR, the area including Rosie's All-American Cafe is a placeholder for future expansion. Northeast of the Tower of Terror are some entertainment trailers that could in theory be used in future expansion. The Theater of the Stars area could also be re-purposed for an attraction, though I'm doubtful they would have to demolish the theater at any time in the forseeable future.
Also, many Studios buildings are semi-temporary and could easily be demolished, so just because there's a building in the way doesn't mean it's not an expansion plot.