Can't seem to find satellite view with SWGE construction... but here are some of the expansion pads for DHS:
1) SWGE berm: the land between SWGE and MMRR has enough room for a 3rd giant attraction in the land
2)SWGE Triangle: In the south west corner of the park there is a little triangle bordered by SWGE, world drive, and the entrance road to DHS
3) BatB land: Basically the BatB theater is on an awkward diagonal that takes up a ton of room. The theater could be moved/ rotated and open up a fair amount of space for expansion
4) Backstage: A huge section of back stage area that used to be used for the studio tour, but is now just offices. The offices could be moved elsewhere and the park could expand. This is the land between Animation Courtyard and RnRC
5) North of Lightning McQueen Racing Academy (LMRC? never seen anyone abbreviate it): Large forested area north of the Academy that could be expanded onto. would require moving of some backstage roads
6)Indy Parking lot: Basically the parking lot behind Indiana Jones Epic Stunt Spectacular was almost used for Star Wars. This could either be a demo of the show with expansion, or a demo of backlot express to give access to the lot.
7) Area between ToT and Fantasmic: some backstage stuff going on, but already has a path going right next to it.
I'm sure there are more, but that's what I know.