These dates are much more realistic considering the scope of what they are doing:
Marvel Studios Feature Film Pipeline
Film/Character - Prior Release Date - Current Release Date
IRON MAN 2 - May 7, 2010 - May 7, 2010
THOR - July 16, 2010 - June 17, 2011
THE FIRST AVENGER: CAPTAIN AMERICA - May 6, 2011 - July 22, 2011
THE AVENGERS - July 15, 2011 - May 4, 2012
Spider-man 4 - May 6, 2011
Avengers moved out a year. Let's make it right Marvel. No corner cutting.
Marvels web site announcement