Supposedly Hoopa gets Impractical, attacks don't hit him every other turn
Diancie gets an ability that boosts special moves in clear skies
Volcanion's "Steamed Up" gives a 1.4 multiplier to his stab moves
Like I said I haven't seen the source on these & I'm willing to bet they're as fake as those bsts and junk that were floating around before (mega latias would be dragon/fairy; mega latios got adaptability etc)