Looks like they added an e-sports multiplayer function that allows for in-game commentary. By the looks of it, its going to be a live thing and not just an add-on to the theatre mode.
Riot Shield being deployed and used as cover a-la Gears of War. Tomahawk is back. Not sure what to make of the pistol and knife class. We'll have to wait for the usual youtube commentators to dissect the trailer further. I'll be back later with more after I hear what the others have to say about the trailer.