MCV features a preview tidbit from an interview with Christoph Hartmann they will publish in full tomorrow. They quote the Global President of 2K on the potential for multiple BioShock sequels, and while he stresses they don't plan to "cash in" on the underwater shooter series in the manner of The Matrix sequels, his reference to the Star Wars movie series recalls another franchise that arguably did just that:

For Bioshock, because it’s so story driven, the question obviously arises: how long can you do it without turning into The Matrix? The first Matrix was great, the second one was weird and the third one, you thought: ‘Who [making this] is on crack and who isn’t?’. “But, then again, look at Star Wars. It’s a fight between good and evil, just like Bioshock. If we spin it the right way and get the right twist of innovation, we can make six parts of it, as Star Wars did.