I hope that it's a character we haven't met yet. People have been theorizing that he has been cast as Bae, I for one don't think so. He looks nothing like what I think adult bae would look like.
Plus I think adult Bae is the mystery man at the beginning of season 2 episode 1. I dunno at this point the guy could be cast as anyone. I for one am almost always wrong when it comes to guessing, so we'll just have to wait and see