They're going to move that road over, and put a 4th resort on the land next to the RPR.
A 3rd park will dilute the others. That's why I don't care about Disney that much. You have to visit 4 parks, each one only having 2-3 thrill rides.
They've got a huge space of land at IOA next to Rip Saw Falls. And the rumor is they'll build the flyer around the Discovery center. At USF they've got a huge piece of land behind MIB.
But the real issue is maintenance costs. Parks take out an old attraction, and replace it with something new. So the issue of running out of land doesn't matter.
At IOA, Triceterops encounter is done, and will be replace with the flyer.
At USF, BTTF should get the axe and be replaced with something new.