That was confirmed last page... lol. Anyway, more Serebii stuff!
Pokémon - CoroCoro Reveals
Clearer images of CoroCoro have been posted to Japanese forums and this batch showcases more information about Diancie. Specifically, it reveals that Diancie's ability is Clear Body, and states that it can learn moves like Hyper Beam & Explosion, and showcases the new movie poster featuring Diancie with details saying that the movie is "A grand adventure with the princess of the Diamond Mine Country". Not much else is known at this time
Edit @ 07:03: A new distribution event has also been announced. Within next month's CoroCoro, a special Serial Code is to be released. This Serial Code, like the Garchomp one last year, provides one-time access to a special Charizard. If you are playing Pokémon X, it will give you a Charizard holding Charizardite Y. If you are playing Pokémon Y, it will give you a Charizard holding Charizardite X