Not to rain on anyone's parade, but if the Uni/Disney contract does indeed say something to the effect of, "If 'Character X' was ever a member of The Avengers, they cannot appear in an American Disney park east of the Mississippi", then Guardians of the Galaxy will never appear in Disney World. The GotG were made honorary members of The Avengers in the late 1970's. Now if Disney really wants a GotG attraction at WDW, I'm sure they've considered lawyering-up by saying, "But they were only 'honorary members', not 'real members'!" I don't know if it's worth the cost, but just sayin'.
Oh, and here's my source: Marvel's official list of every superhero who has ever, at one time or another, been a member of The Avengers:
http://marvel.com/universe/Avengers
Relevant quote from the page: "the group attracted associates such as the aging speedster
Whizzer,
Wonder Man, the robotic
Jocasta, the time-spanning 31st century
Guardians of the Galaxy, and
Ms. Marvel (later Warbird), all of whom helped the team oppose the mad man-god
Korvac and his wife
Carina."