Bioshock's Designer's "New Project"
Ken Levine and his team were part of the group working on the first Bioshock. However, they are not working on the sequel Bioshock 2; instead they are focusing on another ‘ambitious’ title.
While speaking to game site Gamasutra, Levine said: “And when we thought about the shipping date of the project… We needed a certain kind of length for the title, because we had a scope and ambition in mind which is more ambitious than anything we’ve ever done.”
“Even more, substantially more ambitious than BioShock,” he continues. “And we knew that was not going to happen overnight.”
It seems like Levine’s team is working on something big, really big. But we are unlikely to hear anything about it for a long while. We will just have to wait and see.
[Updated - Ed]

Source: http://www.kotaku.com.au/2009/07/bioshock-designers-new-project-more-ambitious-than-bioshock/