From the sihlouette, I'm going to safely predict that it could very well be Mightyena's evolved form. Although it could very well be a brand new Legendary Pokémon, seeing that it's the "key" in the 13th Movie. If it is a Generation V Pokémon as speculated, then the National Pokédex numbers for the Three Starters of Generation V will, more likely than not, be 494, 497, and 500 respectively, with the Grass line taking 494, 495 and 496, the Fire line taking 497, 498 and 499, and the Water line taking 500, 501 and 502.