Ken Levine designed BioShock, but he's not involved with BioShock 2. He and his team are working on another title, a very "ambitious" title.
Levine tells game site Gamasutra, "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."
Sounds like this will be big, and it sounds like it's something we won't see for a long, long time. Be patient!