Disney has no need whatsoever to build a fifth gate at any point in the near and not-so-near future. Right now, they only have enough content for three actual parks that currently happens to be spread out over four physical properties. The recently announced expansions will hopefully change this so that, once they are complete, for the first time since Animal Kingdom's opening, Disney may actually have four full parks. But the date for this is a long, long time away. And there's plenty of room at most of the parks for additional expansion, anyhow. An entirely new park would be cost prohibitive at this point and unnecessary. Disney's more interested in filling the existing properties with people to buy food and stuff - and building timeshares. Universal, on the other hand, would find a way to open a new gate if they had the land. Whatever they come up with has a shot at being ingeniously creative, along the lines of the Hogwart's Express transport between IoA and Universal Studios. So, my guess would be a Universal third gate prior to a Disney fifth.