From Serebii:

"Online and wireless battles in the games remains exactly the same as before. While between Pokémon Omega Ruby & Alpha Sapphire games you can do and use anything, when you connect with players of Pokémon X & Y, there are several restrictions. Essentially, you cannot use any of the new Mega Evolutions, new moves and new abilities in battle against these players. The game will inform you as you select your team whether or not it can be used."

So... are we still sucking on GF's cock?