There goes Islands of Adventure.
1) Universal has exclusive rights to the charactes in theme parks on the east coast, so any attractions will likely be Disneyland based, at least according to what Universal was saying when Disney bought Marvel. Their contract has a few years left on it.
2) Marvel is only one of, I think, five "islands" at IoA. And it's NOT the most popular even, not since a certain British magical schoolkid moved in. Potterland is already in the midst of expanding: they are connecting Potterland to Universal Studios, the other park. The area that used to be the Jaws ride is becoming Diagon Alley, complete with train to shuttle you back and forth.
3) If (when!) The marvel contract ends, I expect universal will make a STRONG pitch to WB for the DC characters. I imagine universal can offer them more $$$ than Six Flags, after all.