With the Star Wars Land and Toy Story Land expansions, my next focus would be on Animation Courtyard, because I feel that area is underused. Not necessarily to make it another Fantasyland, but I think with the park moving away from a studio vibe, you could have the land/miniland be a different style of Toontown, perhaps a blakc and white toontown to fit the 1930s themes of Hollywood Blvd which it branches off of. And perhaps connect it to the backside of Sunset Blvd as well to create better guest flow than having a dead end.
I also think a parking garage like at DTD would allow for more future expansion space down the road.
There's a large, open area right in front of the Great Movie Ride/Chinese Theater that, personally, looks way too open. The space there could easily be filled by, say, a massive Sorcerer Mickey cap? I don't know, just spit balling ideas here.
In all seriousness though, if Disney could bring back the actual Studio element of the park, like, actually making movies, that would be amazing. Unfortunately, I don't think it is logistically possible or feasible.
Has anyone ever seen the Chip N Dale cartoon "Two Chips And A Miss"? For some reason I'm imagining a 1940's/1950's style Night Club restaurant based on the cartoon.