Seriously though, I think there's a little bit of a deliberate shell game going on here, what with so many mysterious non-book accurate characters floating around. Obviously going in they know the audience is going to be on the look-out and trying to guess when and where the giant eyeball bloke is going to show up, so it's not surprising that they'd use some of these characters as red herrings.
Of course just like an actual shell game, it's only a short-con, so they shouldn't be keeping it up for long. It's only a matter of time until Annatar shows up.
Going into this, I rather assumed that he'd already be in Numenor, Wormtongueing up the joint (now there's a vivid mental image . . .) But unless they're going to pull a switch with Pharazon being Annatar the whole time, so far that doesn't seem to be the case. So if they're going to stick with closer to the book version of events, Sauron is currently in Mordor, and will be captured and brought back to Numenor.
That seems to imply that Adar is the prime suspect . . . but I don't think so. I think it's more likely that we just haven't seen Sauron show himself yet, in any guise.