Iron Man 2 has been announced for released on April 30th 2010.
It has also been confirmed that the movie will be used to introduce Thor which is due for release on June 4th 2010.
The First Avenger: Captain America will be out May 6th 2011 followed by an Avengers movie in July 2011
http://www.superherohype.com/news/topnews.php?id=7165