Good evening, gents. Grandson of John Gamefreak here. Have a bit of info on ORAS I'd like to share with you.

22 new megas confirmed aside of Diancie and Sableye, they are as follows:
>Cacturne, Nidoqueen, Nidoking, Blissey, Zebstrika, Whimsicott, Lilligant, Sudowoodo, Crawdaunt, Salamence, Ambipom, Electivire, Magmortar, Mamoswine, Frosslass, Ledian, Xatu, Azumarill, Gallade, Frosslass, Metagross, Kingdra

14 Primal regression/megas confirmed as well aside of Groudon and Kyogre, they are as follows:
>Rayquaza, Dialga, Palkia, Kabutops, Omastar, Genesect, Jirachi, Deoxys, Armaldo, Cradily, Mew, Regirock, Regice, Registeel

Battle Frontier doesn't make a return. It was axed for a new thing called the Battle Mezzo, which is actually kind of cool. Essentially, you connect to the Battle Mezzo and compete in a big wifi tournament throughout the month. At the end of the month, the 7 players with the most points become Champions in basically a Battle Frontier-esque setting (though theyre NPCs with the team they won their last game with).

Pokemon Amie doesn't make a return either, but there is a kind of Amie-styled game where you can wash eggs, cradle them, etc. You can put the mother or father in there too, which will do the same thing as manually playing them. Its meant to increase the chances of better stats/EVs/IVs/etc and halfs the time of hatching. Forget the name of it for english but in japanese its called Pokencubator.

Contests make a return. Pokeblocks can be made with 4 players on wifi.

Steven Stone has a Mega Metagross. It has a new ability called Pedal to Medal (jap name, not sure on english yet) which gives steel type moves priority.

Wally's Ralts evolves to become a Gallade in OR, and a Gardevoir in AS. Both have Megas. He's also around in all the Steven Stone storyline parts.