EDIT (5:00 PM): I mistook the poster in the upper right hand of the puzzle packaging as this page from CoroCoro (guess that’s what happens when you write a story at 2-3 in the morning). It is now very likely that there is a new Pokemon behind those white boxes, at least if the evidence turns out to be true to what it says.
A set of new Pokemon jigsaw puzzles has possibly provided more evidence to suggest that at least one new Pokemon will premiere in Giratina and the Bouquet from the Icy Sky, Shaymin. The manufacturer product image of the puzzle packaging was released on the internet just last night. Each puzzle package comes with one random puzzle out of a possible six. On the product packaging, each of the potential puzzles you can receive is shown.
As you can on the product image to the right (click it for a larger image), two of the puzzle image previews have white boxes covering part of their images. What do the white boxes say? “A New Pokemon Makes Its Appearance!” Since Giratina (both forms), Shaymin, Dialga, and many other Pokemon associated with the movie are shown on the product packaging, the Pokemon being covered up is probably new,
although the next paragraph could disprove that. Although this evidence seems solid, it should be noted that the top right image that is covered up is actually a puzzle of one of the movie posters that has already been revealed. Behind the white box covering the image is Shaymin, meaning that for that puzzle, the “New Pokemon” is not new. Covering the top right image may just be a mistake, with the bottom puzzle (showing Pikachu running) actually containing the new Pokemon. However, if the manufacturer thought Shaymin was new and covered up both boxes because they contained it (without seeing the other Shaymin in the bottom right puzzle image, which is not covered up), this “New Pokemon” speculation could be a mistake for this particular product. Come June, we should know if these puzzles actually have a new Pokemon, but until then, we can’t know for sure!