Here is an excerp from a Feige interview:
Feige: If we do an Avengers 2 it will be after [Iron Man 3, Thor 2, Captain America 2]. They have to grow, they have to change. What they’ve gone through in this movie will impact their state of mind and where they stand in their next movies. Then whatever they go through in those movies is going to affect where we meet them in the next Avengers film. But I think people will be surprised to see, as we go forward – particularly in Iron Man 3 – the notion of how singular the stories can become. Iron Man 3 is a very singular Tony Stark story. As is Thor 2. Cap, who is stuck in the modern day with no friends or family, there will be some revelations of who is still alive from his days in WWII, but SHIELD and Nick Fury are kind of his confidants right now. So of all these movies, Captain America 2 will be most closely associated with Avengers.
Add this to the list of what we know!