Mega Diancie, possibly with a new Ability but with the same type as before. Mega Sceptile is Grass/Dragon now, Charizard style, only with a near-useless ability in Lightningrod (already quad-resists). Mega Swampert stays the same typewise, but gets ripped. No new streamlining but apparently its ability is Swift Swim. No Sap Sipper for you.
Not much new information concerning Mega Groudon and Kyogre.
A bunch of Hoenn characters are also shown to be returning with minor redesigns but bluh images. Go to Serebii. :\