I originally had this movie pegged at around $250 - $265 mil domestic with no shot at $300 mil and definitely no shot in hell in topping Iron Man. However, a couple of weeks ago, I kind of felt that it could get up to $275 mil. Now with the more I see (commercials) and read and getting hyped for it myself, part of me thinks this movie actually has a shot at topping $300 mil.
It would be quite an amazing accomplishment to have two superhero movies gross more than $300 mil in the same year. I hope it happens.