Kyurem King Forme, a humanoid Ice/Dragon pokémon with Snow Warning as its ability, Sacred and/or Secret Sword added to its movepool and no charge-up turn for Ice Burn and Freeze Shock while at this forme; it changes to King when taught either of these moves.
You heard it here first.
And yes, after looking at this, I'm 102% sure Kyurem will have at least one alternate forme. They did the same with Rotom, Giratina and Shaymin in D/P, after all (people only found out when Platinum was released but eh, no one really expected it). Besides, Kyurem is so clearly incomplete one does not even need to be genre-savvy to know what's coming (WINTER).