I didn't expect to hear anything about the next BioShock this year, but 2K went and proved me wrong by including a short teaser trailer in the PS3 version of the first game that unlocks when you beat it (according to Joystiq). Have a watch at this shaky-cam version.
Hang on while I go add "Sea of Dreams" to the BioShock 2 wiki page.
There aren't a lot of details to glean from this thing, other than, obviously, the trailer is set on the Atlantic Coast. (I guess they mean the eastern side of North America? All references to "Atlantic Coast" on Wikipedia refer to North America, even though it's not the only continent to border that body of water.) Previously some rumors had sounded like BioShock 2 would be a prequel that details Rapture's earlier, headier days, but the little girl holding the big daddy doll ought to dispel that notion. There would be no need for big daddies to exist before Rapture came about, and...
Hmm, I guess I should stop in deference to those PS3 owners among you who haven't actually played through the game yet.
What the heck do you think is going on in this trailer? What's this game about?
EDIT: Somebody else updated the name of the wiki while I was writing this. You people are lovely.