Hey, I found this looking around the AC wiki. Endgame spoilers follow.

Video contains spoilers en espanol: Skip to 19:05 or so, and at about 19:09 to 19:11, is that not totally Desmond walking behind the fire? I guess it could be a random civilian spawn (though that definitely looks like his hoodie and bag) or a random glitched spawn of the Desmond model, but given the abruptness of the ending and all, as well as the weird tone that plays when he walks by, could this possibly have some sort of story significance? I tend to think that perhaps it's just an easter egg, but I wanted to see what others thought.

Its not him. Random NPC spawn thing. 

O_O isn´t a bug or glitch? Because he is indeed Desmond

I'm gonna call that a glitch. Shocking in such an otherwise polished gem of a game.

I think the real best part of the epilogue is that you can do Homestead missions where Achilles dies again

"Don't mind me, I'm just breaking the rules of life, death, and time. Figured I'd get them all out of the way in one go. 'k, bye."