View attachment 8557 It's worth noting that what appears to be four large spikes separated into sets of two (on its head) are actually many smaller spikes that look very similar in shape to those of Zygarde. As poor as my highlighting effort in paint is, you can actually see the small spikes side-by-side if you zoom in on the part of the image where lightning illuminates the silhouette. They seem to be behind a vaguely diamond-shaped head, so they could also be protruding from the back of its neck, where the skull meets the protruding neck element. It also seems to lack a clear division below its waist (which would indicate the presence of legs), so it could either have a serpentine or root-like lower half, the former linking it to Zygarde, or the latter possibly implying Xerneas' involvement in the transformation
Yeah, its already been guessed, and likely confirmed that this is Zygarde's true form/state, or just one of the two. No way that this is a super brand new non-forme Pokémon. Still a bit too early for that because there are still things to be wrapped up in Pokemon X & Y.