Here's a bit of explanation from Ben Feder, Take-Two CEO.
The decision to shift a release date is never an easy one, especially with a product as highly anticipated as BioShock 2. We felt that it was essential to invest the additional time to ensure that this title will deliver what its fans expect and deserve. As a result, we will now be launching sequels to several of our strongest franchises - including BioShock 2, Mafia II, Max Payne 3 and Red Dead Redemption - during the next fiscal year. These titles will anchor our lineup for fiscal 2010, and along with other products planned for next year, provide a platform for enhanced financial performance in what we hope will be an improved retail environment.
The company has a conference call scheduled in a few minutes to address this announcement, so we'll pass along any further insight into a specific release date they might offer.