In The Games Department
Pokémon X & Y - Mega Evolution Clarification
With the official Japanese site update, a small note came out regarding further clarification on the Mega Evolutions. Within this site, it details that with Mega Evolutions, you can only have one Mega Evolution Pokémon in battle. It's not known whether it's talking about all of the battle, or just within your team. This is presumably to allow for a specific balance in the Pokémon. It also clarifies that the Pokémon will revert after the battle has ended, not within it itself when the battle finishes. We're still not 100% on the specifics of this new process, but we'll keep you updated as more information comes
Edit @ 17:14: During the VGC Opening Ceremony, Junichi Masuda revealed a new Mega Pokémon, Mega Kangaskhan. It has the ability Parental Bond that allows its attacks to hit twice. We'll have pictures and details as soon as possible. Picture thanks to @pklug on Twitter
Pokémon
http://www.serebii.net/index2.shtml
More details on Mega Evolutions and Mega Kangaskhan!