The following Pokemon were seen in the trailer so are assumed to be part of the local Pokedex for the new region. This list includes evolved forms, as is the norm for local dexes.
Pichu, Pikachu, Raichu
Ralts, Kirlia, Gardevoir, Gallade
Pansear, Simisear, Panpour, Simipour, Pansage, Simisage
Litwick, Lampent, Chandelure
Dratini, Dragonair, Dragonite
Fennekin Chespin Froakie Yvetal Xerneas