Mega Gallade, Camerupt and Sharpedo Confirmed.
http://www.serebii.net/corocoro10142.jpg (Unsupported image host)
http://www.serebii.net/corocoro10144.jpg (Unsupported image host)
http://www.serebii.net/corocoro10145.jpg (Unsupported image host)

Mega Camerupt is confirmed with the ability Sheer Force, decrease with Speed and Boost in all other stats.
Mega Sharpedo is confirmed with Strong Jaws and a boost in all stats.

Primal Groudon and Kyogre have new abilities. Kyogre gets Sea of Beginning which creates a Strong Rain and Groudon gets Land of Ending which creates Strong Sunlight. No confirmation on how it differs from regular rain or sun. Groudon is confirmed with a new move Cliff Blade. Kyogre also gets a new move, but nothing else about it is confirmed.

Mega-Sharpedo might get some plays now, Protect with speed boost then mega for some strength and get those Crunch and Ice fang off. Especially Crunch getting a nice 160 with ability and stab.