Marvel Studios doesn't waste any time.
After Iron Man opened at over $100 million, they've already announced the premiere date of Iron Man 2... April 30, 2010! This is less than two months before the premiere of Thor, which is scheduled for June 4, 2010.
The following summer, Marvel will release Captain America on May 6, and The Avengers in July.
(For those of you who don't know The Avengers, they're Marvel's superhero team-- kind of like The Justice League of America-- that originally consisted of Iron Man, Thor, Ant-Man, Wasp, The Hulk, and-- eventually-- Captain America. The Hulk's movie opens next month on June 13.)