Major spoilers from the previous games ahead, good for a re-cap or to get you up to speed if you never played the others.
Say what you want about the Desmond sections, gameplay wise but I thought this was a really well produced trailer. It's about time we heard something about Desmond's part of this game! I honestly thought they'd skip out on his part entirely for the marketting push.
Additionally, I'm not entirely sure, but it sounds like William Miles is played by John de Lancie.