Bioshock is an incredible game and I really loved Bioshock 2 but I really doubt they can squeeze much for from the Rapture setting yet again at this stage. Where do you think any future games should be set? A different failed utopia in the same way System Shock 2 takes place on a different ship to the original in a Jurassic Park 'there is another island' style twist? Or go in the Half Life 2/Crysis 2 direction and make the whole thing global, possibly where the discoveries made in Rapture became known to the rest of the world and have had catastrophic effects? I think this is what they should have done in the first place when making a sequel. Half Life 2 didn't have us in Black Mesa once again.