It looks like someone at 2K missed the memo. After confirming last week to Joystiq that BioShock 2 had dropped its Sea of Dreams subtitle, 2K has now unconfirmed the news to Eurogamer. So, to reiterate, the full title is, in fact, BioShock 2: Sea of Dreams. It's a shame because we were really hoping to pitch a new subtitle. Alas, it looks like BioShock 2: Big Daddy Day Care just wasn't meant to be.
Joystiq will be spending some quality time with the game in the very near future. Stay tuned.