1)yes it's a dudeA Melkor cultist ( and not even a dude )
2) Sauron was the High Priest of Melkors cult, that guy's clearly a priest of high authority and might even be connected to the white tree fading just before we see him
3)the guy shows up again at the end of the trailer blowing into his hand, which produces some amber flakes and a leaf that looks like the Mallorn leaves from the old movies, which then floats through the darkness and burns up (which fits his war of destruction against the Elves) while there's a voice over of somebody saying "You have been told many lies about Middle Earth" (which fits the words Sauron used to charm the Numenorians)
It's clearly Sauron/Annatar