And before you ask, "duodecim" is "twelve" in Latin.
Scans from ever-leaky Japanese game magazines confirm that at least two new characters will be making it into the lineup: Final Fantasy IV's Kain and (unsurprisingly) Final Fantasy XIII's Lightning.
But what does "duodecim" mean for the game? I'm hoping that it doesn't allude to the character roster, which in the first game ran to twenty-two ("viginti et duo") once you counted Final Fantasy XII's Gabranth and Final Fantasy XI's Shantotto. Maybe it means that there will be twelve new characters? There are certainly enough in the Final Fantasy stable to fit that concept.
It's coming out for the PlayStation Portable sometime next year. You can check out the scans in the gallery, see a fun video below, and begin speculating about the final lineup in the comments!
Personally I'd like to see what they can do with a Final Fantasy Tactics character. Preferably from the original. Cidolfus Orlandeau or Agrias Oaks could easily qualify for boss status.
[Thanks to everyone who sent in the tip!]