A recent update from 2K has confirmed that the Protector's Trials DLC is on schedule to enter certification at the end of January, while Minerva's Den should be finished up by the beginning of March.
2K Elizabeth made the statement on the 2K forums , saying: "as of today, we're tracking to submit the Protector Trials to certification at the end of January. Minerva's Den has some more work to be done on it still and is tracking to submit to certification in the beginning of March."
Certification means the DLC is essentially finished and is being submitted to Microsoft to clear and release.
The Protector Trials contains six different scenarios in which you must protect a little sister as she harvests Adam from a corpse. Minerva's Den presents a self contained single player story in which you play an Alpha series Big Daddy who must fight his way into Minerva's Den to take out the rogue AI that controls Rapture.
There is also a final Bioshock 2 patch in the works. 2K Elizabeth says " I don't have a final patch list for you yet, either, but one item I know many of you will look forward to: we have fixed mouse sensitivity issues and many v-sync option bugs."
2k announced that work had resumed on the DLC last year , when they also announced that the Protector Trials and the patch would be released for free. Pricing plans haven't yet been announced for Minerva's Den.