The riddler said something like this... "Asides from totem Pokemon and Alola forms, something else is coming and it is heavily advertised ". What do you think this could be? With all the "Z" in Sun/Moon I wouldn't be surprised if Z-Evolution or something like Ash Greninja would actually exist in game.

Proof: It is from the Bulbapedia forums where the riddler is often mentioned a lot. I don't have an actual link so you'll have to find it yourself