2K Marin's only announced project at this point is the troubled first person shooter Xcom that recently saw its release date pushed back to 2013, but they are also working something completely new and original.
This project is currently in pre-production, and work revolves around building prototypes, setting the vision through concept art, and evaluate technology that is to be used. 2K Marin have so far developed Bioshock 2 and the upcoming Xcom, and it will likely be some time until we hear more about their next project.