I believe it's a separate project to Ground Zeroes, or that GZ is just a prologue to Metal Gear Solid 5: The Phantom Pain and that the main event won't be about Big Boss as well. I think The Phantom Pain's star is Liquid Snake. The trailer should be mirrored at some parts (like the Ground Zeroes trailer is,) a clue given through 'phantom pain,' a disorder treated through mirrors. This would mean the arm the main character in the trailer lost is the right arm, hence supporting that it's Liquid. He's in the RAF Halton hospital in Cyprus. This was officially closed in 1995, but the buildings remained until 2008. I think they were shut down for some shadowy Patriot program or something similar (there's a UK flag on the wall, I think the game will introduce the British equivalent of the Patriots (with Liquid being British, it'd make sense), but remained in use for a while after that - if Liquid were brought there in 2005 (the body Snake and Otacon stole was a decoy) then if he's in a coma for three years, it would coincide with the building's demolition. Which could have actually been a cover for the raid we see in The Phantom Pain trailer. Liquid's hair is brown because that's its natural colour (he is, after all, the superior clone of Big Boss.) It was only blonde because of bleaching in the Gulf, which after three years indoor in a coma could return to brown. He's got a bandage over his eye - curious, because Big Boss' eye was gouged out a long time ago. If it really is him in The Phantom Pain, why would he have a fresh bandage over it? Furthermore, why would the trailer say 'Open your eyeS' if the subject is Big Boss? He's only got one. The visions of Volgin, The Boss - they're metaphors for Liquid's obsession with Big Boss. The whale at the end (Moby Dick) is further evidence of that obsession - Liquid's always wanted to surpass his genetic destiny, he's obsessed with becoming Big Boss and more. And when Kojima was asked if we'd ever see Liquid Snake again in an interview by Eurogamer for Ground Zeroes, he dodged the question and subtly changed the topic. I don't know, I've just got a feeling that it being Big Boss is too obvious. Maybe it's outlandish to think it is Liquid, but it feels like the sort of thing Liquid would do. And although I don't really believe this myself, maybe 'Ground Zeroes' is the opening chapter of MGS5 (similar to Tanker in MGS2 or the Virtuous Mission in MGS3) and it'll foreshadow what's going to happen in 2008 with Liquid.