Missed it myself, but there was a Samuel L. Jackson cameo as Nick Fury after the end credits of Iron Man inviting Stark/Iron Man to join S.H.E.I.L.D.
 bad phone cam on youtube.
All rumours at the moment... But there's a lot of speculation over on the TIH and IM discussion boards on IMDB.
No, I think the last Captain America got shot in the head or something.
Granted, nothing is ever set in stone, but how would they be able to market a film with a character like this?
Could be a good opportunity for an X-Men tie in though, lets they get rid of all the other guff actors and keep wolverine
Apocalypse should be the bad guy for xmen 4 if they ever do it.
And as for xman travelling back in time, that could be any of them, but you might be talking about Cable.