I'm hoping for at least four game characters to make some sort of appearance.
Looker : I really enjoy this character and it was nice seeing him in Unova. Since he's with the International Police he's not really tied into a specific region.
Fantina : In Sinnoh, it was stated that she was a foreigner so what better region for her home than this one base don France? Who knows, maybe Contests even return to the games.
Juan : Similar to Fantina, he has a French vibe and according to Bulbapedia he speaks French in the manga.
Cilan : This one is mostly for the anime but If XY takes place right after BW2 then, then the Striaton Gym is closed for solo training. So if it's not Cilan, Chili or Cress could appear training. --- "The answer to a question I never asked." - Bridget Tice