I guess I can step in here. The priority to expansion is dealings with Anaheim, and nearby cities.
I can tell you that there is not just one Master Plan, but they do have an Anaheim/nearby cities wish list. Later this year, Disney will file the minorly revised Eastern Gateway plan, and depending how that goes, Disney would love to shuffle things around. One big issue is the Toy Story Lot, which is only temporarily zoned for parking (It is still zoned for agriculture). If that can be worked out (the city want to build the Gene Autry extension), that is another major puzzle piece. Disney is looking for more space away from the resort for BOH Support stuff. They have talked to a property manager for a large property near me (think I-5 and Manchester), not should if it has gone any further than a first talk, but does show Disney has been looking.
Disney is also watching the situation with Angels Baseball, in case that fails to be worked out. (Personally I am 90% sure it will go through).
So yes, a Master Plan would be wonderful, but the Western Structure/Hotel changes messed up a bunch of plans, and everything has been in flex mode since then.
But in Disney's mind, any Theme Park development will only be in the current DLR Specific Plan land. So the key is to move as much as possible to other locations.
Heck, when USCIS moves out (Eastern Gateway land), you might not see it turned into parking, but something else.