I doubt it, if you saw the 2080 you would quickly realize it is a 3 slot card and the heat sink on it is massive (twice the thickness of a standard 10xx series card
is it possible ? once you strip everything off the card ad are down to the bar cpu and mounting holes, if your lucky the holes will line up but I have serious doubts.
and even if it did I doubt that the heat sink of a 1080 is sufficient to manage the heat dispersal of a 2080 card.