Rumors are spreading about three event legendaries more revealed, did someone point this here? Source (Spanish)
Remember 3DS encryptation hasn't been broken yet, so unlike DS games, there could be still hidden Pokémon into the game data.
Supposedly, their names would be:
719 Diancie (ディアンシー), Rock/Fairy
720 Volcanion (ボルケニオン), Fire/Water
721 Hoopa (フーパ) Psychic/Ghost
This info matches some pokémon list filtered back in July. See every Pokémon in that list was revealed eventually, except Dianshii (Diancie), Borukeriion (Volcanion) and Fuupa (Hoopa). That list is completed with Japanese names of Quilladin, Frogadier, Dedenne, Bunnelby, Meowstick, Chessnaught, Zygarde, Delphox, Greninja, Furfrou and Braixen. Note that at that point, only Meowstick was revealed among that list, and Zygarde wasn't even discovered until someone ran into its cave while playing.
This info was already validated by Hiro, leaker of Fairy type and involved with Wottergate.
If this turns to be true, Water would be the second type (after Flying) to be combined with every other existing type. Though a Fire/Water is definitely something I want to see.