Kevin Feige told D23 Magazine (via IGN),
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, Dr. Strange, and the magic side of the Marvel Universe. There are many, many stories to be mined.