I think a Star Wars Land and a Cars Land would go well inside HS. If you look at HS from above they could move that one (main) entrance for parking out to the other side of the canal and have plenty of room.
I really wish Avenue of the Americas was something more (or gone) - it's just so weird. It'd be fine if it were a working set that you could go through when they weren't filming but it's just a dead area. Backlot Tour is kind of blah, too. I bet that would have been far more interesting when it was a real Backlot Tour.
For Epcot: Future World needs some help. Imagination, Sealab 2021, and Universe of Energy could use refresh. Captain EO could just go away and no one would miss it.
Even without sponsorship, they really ought to add in some more countries to World Showcase. The last one was, what, 25-30 years ago. It's mostly just restaurants, anyway. Put in a few countries, add a boat ride or two (Rhine in Germany - you already have plans - just finish it) and call it a day.
Outside of that, I think that they could use a 5th gate. It's pretty much consistently busy down there where adding a 5th gate would basically be printing money. Maybe a boardwalk theme (something like DCA but for the East Coast) or something of that manner.