Team Fortress 2 went free-to-play last year, and with the game to never really stop gaining momentum, the TF2 team have kind of announced their working on something "brand new" for 2012. They can't say what it is, but it's said to be "really cool."
We should also expect the last "Meet the Team" short, where this year, Valve finally unleash the Pyro story. What to expect from that? We don't know, but in Valve fashion, it should be pretty epic. Finally, there's also The Second Annual Saxxy Awards, with this years awards being bigger and better, due to the imminent unveiling of another secret.
What do you expect from Team Fortress 2? Maybe an announcement of a new game mode? The announcement has to be contained within TF2, in my opinion. I wouldn't mind seeing a next-generation Source engine with Half-Life 3, as well as sequels/huge upgrades to their famous games such as TF2, Left 4 Dead, etc.