Re: Who should be the villain in an Avengers sequel? (Poll)
Well, I'd only want that many movies if they are going to continue making quality, the second they feel like they don't have to live up to what they've previously done they should stop.
That being said, I don't think that'd be the case, by the time a 6th movie rolls around their universe would be so firmly established I'd have no problem if they wanted to introduce Alternates to the original team. Whether they don't have them for that movie, or they "retire" -IM for example- from active avenging (still with his solo adventures still i'd hope) I think it could be done.
It's all about execution. I'm sure it could be done in a satisfactory way if they wanted to go that route.