What if Masterchief is actually talking to himself at the beginning of the trailer? His body language kind of aims for that.
"This........is this what you wanted? Is this what you were looking for? Is everything you compromised, EVERYTHING you've done worth it?" *Looks up at Masterchief statue* "Was it?" *Looks down at Locke* "You've completed your mission, Spartan Locke........Mine is just beginning."
So if he really is talking to his self at the beginning asking himself these question then I have a feeling he found out something the ONI is doing that he is trying to stop. Maybe even UNSC and he is betraying them for the greater good.









