Disney's a big corporation but they don't have the power of eminent domain. If (if!) they ever attempt to grow the Anaheim property beyond their current holdings they will pay an absolute king's ransom for each and every square foot.

Besides, reading the actual plans it's pretty clear that Disneyland Forward is more about repurposing and optimizing their current space rather than a "massive expansion" as you call it. Really feels like you're just making up a situation in order to "both sides" the issue.