Nerd Leaks has done some searching and found two trademarks filed today by Nintendo. Pokémon Moon and Sun were found on a European site. Both games have a logo associated with them.
It’s not entirely know what platform(s) Moon and Sun will appear on, if it is a new generation or a sequel to Pokémon X/Y. Tomorrow they will be revealed during a 5 minute Pokémon themed Nintendo Direct with, hopefully, a platform attached.