Ooo!
I just read up on Bulbapedia that the third Generation IV game would be revealed next month. Also, there have been two new pokemon made avaliable for Merchandise, though they don't have names as of yet, they are simply known as the mystery pokemon, "Pokemon A" and "Pokemon B"
What this could mean is that the thing you see in that picture, could be a new legendary Pokemon to the third game, much like Deoxys was added into Emerald. Or it could just be a regular Pokemon, but I have a good feeling it'll be in the third game.
So it seems that there'll be two new Generation V Pokemon in the movie, and possibly the third Generation IV game.
One of which is probably the scary thing seen on CoroCoro