I'm really interested in knowing who is person is.
If you're referring to the Evolution trailer, that doesn't say much because Big Boss was burned to a crisp too. Also if you look closely, he really doesn't look like Skull Face there.
If we're basing this entirely off the Evolution trailer (and even previous trailers), it would appear that Skull Face is indeed the phantom born from Snake's subconscious. He's not real, he's symbolic of Big Boss' evolution into a villain.
But if he is not real, then why do we see him manhandling Huey? And what about his actions in GZ?
That I cannot explain, and what I said could all be unture with regard to Skull Face not being physically real. But let's look all the way back to GZ, "From "FOX", two phantoms were born". We later then see Skull Face with the "XOF" emblem, a mirrored reflection of "FOX". To me, this symbolises the spectrum that Big Boss will explore, a completely changed man, the polar-opposite of what he originally was.
All speculation, but with everything that has been released (Skull Face vanishing in scenes), my belief is that Skull Face is nothing but symbolism of Big Boss' path to villainy.
All speculation, but with everything that has been released (Skull Face vanishing in scenes), my belief is that Skull Face is nothing but symbolism of Big Boss' path to villainy.
I think we need to appreciate that part of the cutscenes (or more precisely at this point, the trailers) that we saw is the real in-game world, some other are Big Boss' hallucinations, and still, there are some others that are meant to be symbolic (i.e. with a specific meaning to tell).
For instance the latest Evolution tralier shown Big Boss from his MGS3, PW, GZ then TPP form and then a heavily burned form (still with the horn on the right forehead) before what we may call the Skull Face form. I think this "time tunnel" kind of cutscene is the symbolic kind, specifically leading us to flashback from a young innocent Naked Snake, gradually being harderned and fallen to become the antagonist we first knew him as. I am guessing, we will see how evil Skull Face (the real one in-game) is, and then at some point, due to his desire of revenge, Big Boss himself became a demon, a kind of Skull Face too. In terms of character design, Skull Face was meant to show that deep inside men, there is no difference of race, but the same skulls (characteristics) in us. I guess that is what is meant to be told here.
Let's not forget Big Boss said in MGS4 that he made some mistakes that Solid Snake, if in his position, would not have made. So it's only natural that we are seeing this kind of cutscenes.
Btw as MGSV's development started soon after MGS4 concludes, I believe by the conclusion of MGS4, Kojima already had some ideas what to tell about Big Boss' fall. In fact MGS4 itself (unless in the rare case of a heavy retcon) has a lot of reference points we can look back to, given its position in the timeline.
I have a feeling that he's a clone of Snake, specially after watching this: https://www.youtube.com/watch?v=nebyCUZ90RA&index=24&list=WL
No, he's not a clone, not everyone is a clone of Snake/Big Boss yanno?
Also, to add in what Wikia contributor 42.98.58.21 said:
The scene starts with Big Boss as how he appeared during MGS3, albeit in his Sneaking Suit, signifying the beginning of the legend. We then go into his appearance of PW, his rise to independence, his own army. Followed by his appearance in GZ, the fall of his army, the birth of revenge. We then see his appearance in TPP, the blood signifying his lust for revenge as flames start to consume him, burning him into a skinless figure, a demon, the results of his lust for revenge. Finally the burned figure, the ultimate result of what his quest for revenge brought him, defeat and near death.
Who is Skullface?
A scrub and maybe the worst metal gear villain to date