This month's issue of CoroCoro included an image of a preview of next year's movie. It has a creature that may or may not be a new Pokemon. caption reads, "!? Is this a New Pokémon?!" Seems like a new form of Zygarde to me.
Well if the caption specifically mentions it being a new Pokemon, I highly doubt it isn't! But I do wonder, does this mean a new Pokemon generation is right around the corner? I wouldn't have expected it so soon, but it makes sense for new main series titles next year at least.