Halo 4 fans will get a chance to see and play the new Castle Map Pack. The Maximum Map Pack will be shown with the just released Gears of War: Judgment. Maximum will be sponsoring the Map Pack.
Microsoft is also planning on showing some cool games for Xbox Live Arcade such as State of Decay, Curse of the Brotherhood, and Motocross Madness; and they will also be showing some titles for both Windows 8 and Windows 8 Phone.
If you want to check out the new Age of Empires II: HD Edition, this will also be the place to do it, with producer Ryan Chaply on hand to provide a guided tour and answer questions. This will apparently be one of the only times that you will be able to play the game before it is released.