The helmet design did change, the cheek area is narrower as well as a difference in the brow, despite that if they matched the Iron Man Mark III version they'd be able to show off the shoulder region which is completely redefined and the coloring over all is more of a cherry/hot rod red than the maroonish color for the first one.
Sideshow confirmed that they'll do 1:1 busts for Iron Man 2 during the last round of open chat but not who or when. My guess is since it took a while for the first one to come out then we were bombarded with three versions I would look to 2011 for Mark IV (Maybe Mark VI) and War Machine with a BD version of at least one.