Eidos Montreal confirmed something called Deus Ex: The Fall in a short little video teaser, that featured tomorrow's date - a hint that we may see a full announcement then.
We currently have no idea of what Deus Ex: The Fall is. It feels a little late for a more DLC for Deus Ex: Human Revolution. But that is, of course one likely scenario - as is a new game. Eidos Montreal are also busy with the new Thief.