Well, since we're being hypothetical and considering all possibilities...let's look at the most recent comparable situation.
Disney buys Marvel...Universal has Marvel theme park rights. Because they are in direct competition with a Disney park, that specific Disney park is not allowed to have the rights...but others are. The closest Six Flags park is in Georgia, and is not in direct competition with Disney (and I suspect keeping their distance from Florida because they don't believe they CAN compete). There are Six Flags in CA, however...and since Disney is free to build Marvel there, suppose they put in a clause on this one that No Disney parks west of the Mississippi can build DC rides. Disney Marvel park in CA, Disney DC park in FL to compete with Universal...whereas a Marvel park in FL would likely not be nearly as much of a value as far as competition is concerned. All the while, maybe Six Flags parks are allowed to keep their DC themes. What threat are they to Disney, really? In California Disney would have Marvel to compete with their DC, and in FL Disney has DC to compete with Universal's Marvel. The rest of Six Flags parks (save Georgia) are so far away, I wouldn't really consider them competing in the same market. If you're really going just to ride a Green Lantern roller coaster and you live in NY, you're not going to WDW anyway.
Maybe i should shutup. I might be giving away Disney's master plan!