You wanted it, here it is -- 2K Games has announced "Minerva's Den," an upcoming single-player piece of downloadable content for BioShock 2.
"Minerva's Den" puts players in the role of an all-new character, teaming up with Brigid Tenenbaum to explore a new area, Rapture Central Computing. The add-on will feature new "high-tech weaponry," along with a new Plasmid. Enemies also get a bit of an upgrade, too -- Splicers now control the elements, Security Bots fire rockets and lightning bolts, and there's an all new Big Daddy type lurking the halls.
2K hasn't dated or priced this final bit of downloadable content (yes, "final"), but it's in the works for PlayStation 3, Xbox 360, and PC.