Good evening, gents. Grandson of John Gamefreak Sr. and son of the late John Gamefreak here. Just got off work, so I have a tad more info I'd love to share.

To reiterate last time's thread:

22 new megas outside what we know:
>Cacturne, Nidoqueen, Nidoking, Blissey, Zebstrika, Whimsicott, Lilligant, Sudowoodo, Crawdaunt, Salamence, Ambipom, Electivire, Magmortar, Mamoswine, Frosslass, Ledian, Xatu, Azumarill, Gallade, Forretress, Metagross, Kingdra

14 Primal Regressions outside Groudon/Kyogre:
>Rayquaza, Dialga, Palkia, Kabutops, Omastar, Genesect, Jirachi, Deoxys, Armaldo, Cradily, Mew, Regirock, Regice, Registeel

Battle Frontier isn't returning. New thing called Battle Mezzo. Monthly wifi tournaments; top 7 take place as NPCs in the frontier-esque battle arena.

No Pokemon Amie either. New Egg-washing/hatching/etc game called Pokencubator.

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

Steven Stone has a Metagross. New ability called Pedal to Medal (again, Jap name). Gives steel moves priority.

Wally's Ralts becomes Gallade in OR, Gardevoir in AS. Both are megas for final battle. He's also present in all Steven Stone storyline scenes.

Now for the new information:

I was mistaken on the information I had seen with some of the Megas (Not so much mistaken as I had not translated some parts up until today). There are actually 27 outside what we know. Appending to that list are the following:
>Camerupt, Sharpedo, Hariyama, Torkoal and Flygon

Volcanian's event for XY is going to be around the same time ORAS is released. When you transfer it over to ORAS, provided you're in post-game, it unlocks another Magma/Aqua storyline where both are trying to get it.

Latios and Latias roam in AS and OR respectively. When you catch them, Steven gives you their respective mega stones.

Mr. Briney attempts to fight off the game's team with Peeko. It uh...ends pretty...sadly, actually. ;_; RIP Peeko

(More incoming)