If I have to guess between the two, I would say X2/Y2 for two reasons.
1. Two games brings more income than one.
2. Zygarde imo is to boring of a pokémon imo to star a game.
What?! I can't hear you over all this awsome! - Pyrrhon (Kid Icarus:Uprising)
Final Ultimate Legendary Earth Power Super Max Justice Future Miracle Dream Beautiful Galaxy Big Bang Little Bang Sunrise Starlight Infinite Fabulous Totally Final Wonderful Arrow...FIRE! - Wonder-Red (The Wonderful101)