It would seem that 2K Marin - the California based studio that gave us Bioshock 2 and the recent The Bureau: Xcom Declassified is being closed down with a large number of the staff being made redundant.
Sources have told Polygon that only the staff that's about to join the recently announced new 2K studio nearby in the Bay Area headed by former Gears of War producer Rod Fergusson are unaffected.
Given that Fergusson helped finish production on Bioshock Infinite and is now being joined by people with Bioshock experience, perhaps the new Bay Area studio is the best bet as the developer on the next Bioshock as Ken Levine has said Irrational Games are likely doing something else next.