Said it in the other two threads:
Oh shit I forgot that Gears of War: Judgement comes out on March 19th. So to me I'm guessing we could see an announcement for the event as early as a week from that game's launch. Microsoft seems pretty savvy about not having any overlap in product announcements and releases so I think it's pretty safe to say we won't see anything before the 19th.
To go into more detail, I bet we're going to see a few surprises from third parties. Possibly Call of Duty X or Battlefield 4, The Walking Dead Season 2, a new Mass Effect or Dragon Age, GTA V, and a few other third party games.