The Halo 4 trailer is quite brief, showing a frantic-sounding Cortana awakening Master Chief from the hibernation he went into at the end of Halo three while their ship appears to be blowing apart around them from causes unknown. The Chief makes his escape from the dying ship's interior, and finally we see some sort of ominous-looking structure out in space that they're heading straight for.
It's not often a video game trailer strikes so close to home for me, with its grim depiction of an emotionally unexpressive guy who rarely speaks just trying to get some rest while a nagging female voice says “Wake up, John!” It's my 13 years in the public school system all over again.
Unrelated side note: I assume that the mist that drifted out when Master Chief emerged from his hibernation pod was water vapor condensing because of the cold from the cryonic whatzit used to put the pod's occupant in suspended animation, but the first few times I watched it really looked like steam to me. Which in turn made the whole scene look like Master Chief had been taking a hot shower, or perhaps sitting in the sauna having a schvitz, while still fully armored. That's a man who takes the need to be ready for action at a moment's notice seriously.