E3 trailer released 40 minutes ago: http://www.youtube.com/watch?v=eF5uXszagcA Watch before continuing to read. Ok, so from what I saw, here are my observations:
Some time after Snake escaped the hospital, he goes to Afganistan to resque Kaz, who has lost his right arm presumably to torture.
New characters:
Quiet, a sniper deprived of her words.
Eli, a youth who curses his fate.
Skull Face, a ghost without a past. (The leader of XOF)
Code Talker, a wise man denied his homeland.
Old characters:
Punished Snake, Naked Snake's his new codename.
Huey Emmerich, a technocrat who stands his ground (now with mechanical feet).
Revolver Ocelot, a rival living a lie.
Psycho Mantis is still not confirmed.
Feel free to post any other observations or speculations about the trailer here.