I can say with a fair amount of certainty that even if the leak is wrong, Chespin will not be Grass/Rock. Because first of all, that completely wrecks the starter triangle*. And secondly... why Rock? What about Chespin makes you think "OMG ROCK IS TEH CONFARMED!!!1"? What, because it learns Rollout? More non-Rock-types than Rock-types learn Rollout. It just gets Rollout because it's a hedgehog, geez.**
Now, if we were talking about a leak that correctly guessed one thing that was easy to guess, then sure, it would be fair to write it off.
Writing off a leak that correctly guessed the names of Helioptile, Pancham (with a small typo, sure), Fletchling, Pangoro, Inkay, Malamar (again with the typo), that Fairy would be super-effective against Dragon, that Sky Battles would exist, that Inkay and Malamar would have a reversal element to them (leak said Inkay would evolve when the 3DS was turned upside-down, and Malamar does look a bit like an upside-down Inkay), that Pangoro would be Fighting/Dark and Inkay/Malamar would be Psychic/Dark, that the first gym would be Bug-typed, that a professor (even if it isn't clear which is which) is named Sycamore... all of this? And you're still going to write it off? Then you're just deluding yourself, plain and simple.
BTW, someone suggested that "maybe the types were switched". Well, actually, they were. Pokebeach initially accidentally posted Grass/Fighting and Water/Dark before getting a correction and fixing it. Which means bad things if you're still hoping for non-Grass-Dark...
* - Yes, yes, I know about Empoleon. Torterra became a Ground-type, though, so it still worked out. Fennekin would have to be part-Ice (doubt it, and it would still be weak to Rock), Bug (lol), Fighting (come, on, haven't we seen enough of that type combo in starters?), or Steel in order to make up for it. Fire/Steel Fennekevo? Well, actually, it's possible, but it's hardly what I'd call probable.
** - Assuming Froakie will be a Flying-type because of Bounce is similarly flawed - actually, very few Flying-types learn Bounce. And Water/Flying does similarly bad things to the starter triangle as Grass/Rock. It learns Bounce because it's a frog, simple as that. --- Creator of Jay's Journey (see quote!) "It's not ten years old! Therefore, it sucks!" - Nostalgia whores everywhere