A bunch of gamers got their copies of X&Y early from small stores and have revealed the final evolutions for the starters. The reveal seems to show that the theory that the three starters represented classical RPG archtypes (Tank, Rouge, Mage).
Delphox is clearly rocking the "Look at me, I'm all magical and shit" look, and her typing suggests it even more. Delphox has been leaked as a Fire/Psychic type. The only precedent for that typing is Darmanitan's special form in Black/White. Delphox could make for a very interesting addition to the fire starter lineup.
Chesnaught's name says it all. She looks like a damn juggernaut and is also sporting a cool new typing, Grass/Fighting. Breloom is the only other Grass/Fighting pokemon that comes to mind. This typing doesn't seem the best, on face. It gives the most weaknesses of any of the three starters, and grants a 4x weakness to Flying. Sorry, Chespin fans.
Greninja has to be my favorite final evolution. Look at that suave bastard! His new typing is Water/Dark, used by the likes of Sharpeedo and Crawdaunt. This typing is badass for the psychic immunity, as well as for resistances to Ghost and Steel. Look out for the typical water wreakers, like electric and grass, but add fighting and bug to that list too.
Now I definitely know which starter I'm going with. Froakie 4 lyfe. How about you?