Well I feel like if Greninja is real GF will officially reveal it within days since its leaked. So if they don't I think that confirms it as a fake.
Also what's up with that name if it's real? Not only does the design bare little to no conistency with the line, neither does that name. At least Samurott kept the "ott" naming consistency. Froakie and Frogadier both have frog in their names, so the third evo should as well.