So... Think about this...
They have revealed Sylveon, Xerneas, Yvetal, and "Newtwo", and yet they haven't even hinted at the types for any of them? Why are they trying to hide the types? I think this could be pointing towards the fact that there are new types. Obviously Yvetal wouldn't be the same type as the other 3, but they would want to add something to him as well, otherwise they wouldve just given us type information already.