If you ask me, Chespin's final evolution is going to be a Pokemon with Fighting as its secondary type. Why? Because it makes sense looking at Fennekin's and Froakie's final evolution. Fire is super effective against Water, so Fennekin has a natural advantage over Froakie.
But on their final evolution they suddenly gain Psychic and Dark types respectively, so suddenly Greninja also has a natural advantage over Delphox, switching everything around. Now wouldn't it make sense for Chespin's final evolution to gain Fighting type, hence giving it that natural advantage over Greninja? Just remember that Psychic, Dark and Fighting form a triangle; just like Fire, Water and Grass.
