It’s a risky move, but they’re probably looking at the finite disposable incomes of the Summer action blockbuster having been significantly depleted with The Avengers and about to be totally depleted with Dark Knight Rises.
When I saw the release schedule for this Summer the first word that came to mind was “oversaturation”. There’s only so much entertainment revenue to go around, so a second/third tier, non-niche action flick like this doesn’t stand a chance. Better to delay to a safer release date next Spring.
After reading #10, I think we have our reason.
Prometheus was scheduled to come out two weeks before and Spiderman a week after. That would also leach a lot of money away.