Well this is interesting.
While Zeraora wasn't in the trailer, we got wind of a new merchandise listing for June of this year and it has a couple interesting tidbits:
According to this, alongside Pikachu and Lugia there are three unknown listings (apparently titled "on-screen Pokémon A/B/C) for Pokémon for release. Zeraora would likely account for one, but the other two we have no indication of who they are outside of speculation. So it seems like we may start hearing about some of the new roster for the game before or during June if this is any indication.
Edit: Also, according to Desdar300 on Bulbapedia, the new girl's name is Lisa, she made a promise to Lugia at one point, and the town has a connection to the wind. Not too much, but at least we got a bit more on her.