Of course, we don't know yet if he is really a rival. Let's just say he is until we know new official stuff.
He's shown battling you using one of the starters in the trailer if you watch carefully. He was using the starter that is weak to yours though, so that might mean there's two rivals again. I'm kinda hoping the second rival is not the player character you didn't choose again, though I guess it wouldn't be too bad if it was so long as their personality isn't too generic.
