I've heard recently that a third Star Wars ride goes in the middle of the new land across from the other two. Back section of Great Movie Ride gets demolished and backstage area gets pushed back into newly created space, allowing more room for third attraction.
I could be mistaken, but I believe DL already has the space, so this was part of the calculation of closing GMR for a smaller ride.
Was going to play the wait and see game before declaring this as fact though. Once we see some demo we'll know for sure.
Regardless, it has always been the plan to convert unused portions of GMR building to backstage, I just figured inside storage or something. But recently rumors have turned to actual demo of back section.