The latest leaks from CoroCoro have begun floating around the internet and has revealed three more mega evolutions to appear in the upcoming Omega Ruby & Alpha Sapphire games. The leaks also reveal some more information about the contests.
The first is Mega Altaria who is a Dragon/Fairy type and has the ability 'Pixilate'.
Next is Mega Lopunny who is Normal/Fighting with the ability 'Scrappy'.
The third, and final mega reveal, is Mega Salamence with the ability 'Aerilate'.
Also confirmed is the ability to change Pikachu's cosplay for contests and that it gets special moves:
Pikachu Rock Star knows Meteor Mash
Pikachu Ph. D. knows Electric Terrain
Pikachu Pop Star knows Draining Kiss
Pikachu Belle knows Icicle Crash
Pikachu Libre knows Flying Press
During the game you will meet a 'Contest Idol' called Lucia. Lucia will give you special clothes for participating in Pokemon Contests.
Finally, a distribution event was announced for Omega Ruby & Alpha Sapphire. You will be able to obtain a Shiny Beldum holding it's Mega Stone. Similar to the release of X & Y with an event Torchic holding Blazikinite.