Well, according to action icon Jean-Claude Van Damme, he's open to joining the sure-to-be-massive superhero sequel, and I'm sure there'd be a lot of old school action fans who'd like nothing more than seeing JC delivering a helicopter kick or two to Thanos, or whichever Marvel villain is foolish enough to get in his way.
Posting the above image of himself and Marvel legend Stan Lee on his Facebook page, Van Damme said: "It was my pleasure to meet Mr. Stan Lee (creator of "X-Men", "The Incredible Hulk" and "Spider-Man") back in 1994, along with Mr. Samuel & Mr. Victor Hadida! I read that Chris Hemsworth (star of "Thor" and brother of Liam Hemsworth, "The Expendables 2") would like me to costar in "The Avengers 2" movie! Well, it would be fun to play one of these types of amazing comic book characters again. By the way, I am a big fan of Marvel's superhero Silver Surfer and also another heroic fictional character known as Doc Savage - the Man of Bronze!"
Somehow I'd be a little surprised if Jean-Claude was top of Whedon's list for The Avengers 2, but surely there's room for him somewhere in the Marvel Cinematic Universe?