Actors need to realize that they have short shelf lives. Once they have momentum they need to keep it. Producers have very short memories.

Apparently, the entire movie industry is in a craze about "extended universes" because of the Avengers bursting out with almost two BILLION dollars in sales! Hence Fox wanting to throw their only two properties together in their own extended universe. (X-Men and Fantastic Four) while poor old Sony is stuck with just Spiderman- and yet, they're even considering an extended spiderman universe with Black Cat spinoffs and who knows what else!

I even read an article on Mad Max! They're considering a Mad Max extended universe? Seriously? It's a movie about one man!

As for Captain America taking a break? Certainly. he can hang up his shield for a little while and train rookie SHIELD agents or something, get trapped in the Hel dimension of Asgard or some other story event to take him out of play for a bit.