Here's what Kevin Feige had to say, also indicating that he wants to spin off The Black Widow, Hawkeye, Doctor Strange, and the S.H.I.E.L.D. organization into their own separate movies.
"Thor will go off into a new adventure, and Captain America will continue to explore the modern world in another film of his own. We hope that holds true for the characters appearing in that film - Black Widow, Hawkeye, and the spy organization, S.H.I.E.L.D. -all of whom are more than worthy and capable of carrying their own films. And, we've got a lot of other characters we're prepping and getting ready for film debuts: the world of martial arts, these great cosmic space fantasies, Doctor Strange, and the magic side of the Marvel Universe. There are many, many stories to be mined."
"X-Men was the dawn of the new Marvel cinematic age. Iron Man was the dawn of the Marvel Studios age and the establishment of the Marvel Cinematic Universe and the beginning of that continuity. The Avengers is the next big step. Once all these characters come together, it's the culmination of all that has come before. It launches a new era and a new time in the history of our films. Not only will it be the first film that our new home studio, Disney, will be distributing, but it will also renew each of these characters and launch them into their own franchises, starting with the second film to be released by Disney, Iron Man 3."