I thought the trailer was awesome, personally, and I'm actually quite interested and optimistic to see how a studio besides Bungie will handle the campaign. (Two words: level design. Four more words: Bungie sucks at it.)
Multiplayer is the only thing I worry about. Bungie has created something special, and I'd hate to see 343/MS fuck it up.
I want to see how 343 does level design as well as how true to the story they will be(Bungie kinda flopped with that). I hope Bungie works on Marathon soon because it is pretty much Halo. Marathon would be the only competitor to a new Halo game.
Although I am a little bit angsty that they are continuing the Halo series, I don't have to play it. I understand that from a business standpoint...it's good buisness to keep making something that sells. I just don't exactly have what could be called high hopes for a game series that's not being made by the same developer that started it. Kind of like how Bioshock 2 wasn't nearly as good as one without the same team.
I'd like to see more realism in the next Halo, with them paying more attention to how harsh the war and fighting is for the ordinary grunts. Obviously I don't want to play as an ordinary soldier, but it'd be nice to get a sense of the cost the war is having on the normal (non-superhuman) soldiers you're fighting alongside.