On the latest issue of Shogakukan’s Monthly Coro Coro, it has been confirmed that Metagross will be have a Mega Evolution form featured in the upcoming Pokémon Omega Ruby and Pokemon Alpha Sapphire for the Nintendo 3DS. Mega Metagross will be used by Elite Four Champion Steven, who evolves the Pokémon using the Mega Brooch.
Pokemon Omega Ruby and Pokemon Alpha Sapphire is scheduled to release for Nintendo 3DS on November 21 in North America and November 28 in Europe. The original Pokémon Omega and Pokémon Sapphire were released on the Game Boy Advance on 2003.
Check out the scan below: