Ideally, no one. At least to me, the BioShock series has been going downhill ever since the first game, and I really don't want to see it get torn down any further, which is all the cash-grab would do.
However, since 2K is definitely going to continue it, I would like them to bring 4A Games. Sure, Arkane Studios would be better, but I doubt that's even possible. After Arkane, 4A Games probably comes to the closest to making BioShock-styled games, and I actually found Metro 2033 to do a better job of capturing the glories of BioShock than any of the sequels have done.
Given the most likely scenarios, though, it will probably go to 2K Czech. 2K Marin hasn't really worked on an impressive game, and they also underwent layoffs after The Bureau released, so they don't seem really trusted right now. 2K Czech has at least been successful, and the Mafia series is reasonably close to BioShock in terms of what they focus on. Who knows, maybe 2K could even get Yager to come in and work on it. That actually might work out.