Although he's stated in the past that appearing in a non-Avengers/Captain America film would be a violation of his contract, Chris Evans and Marvel Studios have apparently found a way to make it all possible. Talking from the Toronto Film Festival, Evans hinted that Captain America/Steve Rogers might show up in the now-in-production Thor: The Dark World.
[Chris] Hemsworth and I even talked about that. I would love to do a little thing in Thor 2. It is obviously going to be tricky trying to work out the plot, the reason why I am not there to help him, and why he is not there to help me. But the best thing about Marvel is that, like I said, the movies were so good and we had such a good time making them.
It also looks like we'll see some scenes that were shot and cut from The Avengers in Captain America: The Winter Soldier. Evan's explains,
The most I am looking forward to is exploring a little bit of Steve’s…they had all those deleted scenes with The Avengers because a lot of those scenes are for Captain 2, you know what I mean? It was good stuff, but it all felt like that was his story. It is a different movie. With The Avengers there was so much to cram in. So I think making it any longer would have just been exhausting. A lot of that stuff [that was cut] is for Captain America 2. That is his story. It is him trying to on a personal level adjust to the fact that everyone he knows is gone and the whole Peggy Carter of it all. There are a lot of things that he kind of has to come to terms with. So I don’t know. I am excited to kind of see flashes of the first Captain, if you know what I mean, and to see his memory of what we now know as an audience of who he was.
Whether or not we'll actually see Evans show up in the middle of Asgard is yet to be seen. Thor: The Dark World will be released on November 8th, 2013 and Captain America: The Winter Soldier will be released on April 4th, 2014.
Would you like to see Captain America and Thor back together again?