Take-Two Interactive Software's Fiscal 2008 Financial Results confirm development of BioShock 2 (thanks Gamer's Hell) at the new 2K Marin studio for a holiday 2009 release:

2K Games said today that BioShock 2, the sequel to the wholly owned and internally developed title, is being developed by 2K Marin and is planned for release in the fourth quarter of fiscal 2009. The critically acclaimed BioShock title has sold over 2 million units worldwide since its launch in August.