If they're building parking garages for studios...I would think that means new traffic flow and possibly an expansion of the "Lucas" area into the existing service/parking lot area.
Even of they don't keep the stunt show, mama melrose, muppetvision, etc...what sense would it make to build over top of it if they are planning on drastically increasing the attendance - which is a given.
MGM was never meant to handle 15,000,000 customers...never. It was a converted EPCOT building with a half cocked Eisner idea to build "Hollywood east". Not to handle fastpass+