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.