According to Rogen, who spoke with Drew from Hitfix.com, its a blessing in disguise:
"We're both relieved and psyched about the change. It gives more time for post, which would have been immensely rushed if we were to come out in the summer. It also affords us more time to promote the film, (now we can go to Comic-Con with more than a car!) and ultimately is a great vote of confidence from the studio. We got the same date that movies like 'I Am Legend' and 'Avatar' are getting, so we're thrilled to be there."
The film hasnt started shooting yet, and in addition to Rogen, stars martial arts star Jay Chou as Kato, as well as Nicholas Cage, Cameron Diaz and possibly Edward James Olmos.