Holy shit! Marvel's The Avengers has exceeded even the wildest expectations and will surpass the $600 million mark at the domestic box office today. It still has a ways to go to catch the #2 film in America, Titanic, but will actually surpass the film's initial domestic take (Titanic made an additional $58 million from a 3D re-release this year). It won't surpass Avatar, but can it sink Titanic for the #2 spot? With a re-release definitely, but for now we'll have to wait and see.
Avengers was the fastest film to $100, 200, 300, 400, and 500 million, doing so within 23 days. It had taken another month to reach the next milestone, and would need to last through at least July to have a shot at #2. Once the final Dark Knight film is released, though, The Avengers run will likely end.