In a recent Captain America update from Entertainment Weekly, they had a name that has never been mentioned before. Sebastian Stan.
Cloverfield’s Mike Vogel, Gossip Girl’s Sebastian Stan; and the unknown, Young and the Restless’s Wilson Bethel. The studio held lengthy screen tests last weekend for at least four of those actors (Hedlund has not yet screen-tested, though sources believe he is the studio’s first choice), and Marvel is expected to have a decision soon.
Sebastian is best-known for playing Prince Jack Benjamin on the television drama Kings and Carter Baizen on Gossip Girl. I'm pretty sure if he is indeed on the list, it's for another character.