You know, I could see the following happening one day... Sea World has been under lots of pressure recently, both from public relations issues and, more importantly, the competition from Universal - Sea World sadly takes a hit before Disney does.
It's not impossible to imagine them wanting to sell the Orlando park one day.
Now, what imagine a day when Universal has cannibalised much of Disney's business, and when we have a Disney CEO who is as keen on mergers and acquisitions as Iger, but has an interest in the parks... I could see them buying Sea World as a fifth gate, rename it, then say to the fans 'well, you wanted DisneySea, here ya go!'.