I went to Disneyland today and took a look at the construction from the parking structure.
Those AT-AT structures are really obvious and are clearly a frame inside the building itself (which is hard to tell from the images as they sometimes look external to the building). They also seem to be connected to the very deep basement level which matches the description of the multi-level ride mechanism that has been discussed before.
I think the round structure that has gone up recently may be the base/enclosure for the Millenium Falcon ride due to its size and shape. Seeing people stood inside it made it more obvious as to how big it actually is.
Rockwork also looks like it's starting to blend in with the existing rockwork in the area towards Rivers of America.