I don't want them there forever. It doesn't stay true, in my opinion, stay true to the spirit of the comic. You have to rotate the roster. Maybe you bring one or both back, but I think at some point some new characters come in and others go out. Since this is an expansive universe we don't need Iron Man or Thor or even Cap for every film. They can return to their own respective films like they do in the comic. Avenger seems ideal place to showcase the characters that can't support their own films. Also look at the success of First Class. Not a popular X-Man in the bunch besides Eric and Charles.