Someone else got their hands on CoroCoro and is talking about it on 2ch. It's getting late in Japan and there won't be any pics until tomorrow (not sure what the deal is) but these are the details:

Primal Kyogre's ability translates roughly to "Primal Storm". It causes rain to last "longer than normal" and boosts all Water/Electric attacks on the field. Primal Groudon's ability is similar, "Primal Sun" that does the same for sun and boosts all Fire/Ground attacks. There are screenshots of them using their new signature moves (same as in the trailer), but it teases information on those for next month's issue.

Mega Regice has Snow Warning, Mega Regirock has Sand Stream, and Mega Registeel has a new ability "Magic Room" (again, roughly, I realize this is already the name for an English move) that automatically summons Trick Room. He says the designs look nothing like the original forms and are very odd. There is a section about the braille puzzle which also hints that Regigigas is in the game with a secret and will unlock a special area.

There is new art of Brawly and Wattson. Contests are back with new features and updates. You can use Pokemon Amie to train a Pokemon's contest attributes with specific food, toys and minigames. Amie screenshots show a different interface and perspective than the one in X/Y.

Apart from that, everything else is what we got from last month during E3 and from the official site update.