Personally, I don't think new Mega Evolutions particularly likely. While they could patch in support for XY, I don't see them doing that. In the past, the only patches have been bugfixes - they've never added in new features.
Plus, there's the fact that ORAS were almost certainly being developed simultaneously alongside XY. If they knew ahead of time that Mega Groudon and Mega Kyogre were going to be important for and used in ORAS, why not include them in XY to begin with, so you don't have to worry about patching everyone's games?
I guess you could argue that they wanted to keep them secret. Okay, why? How would a Mega Kyogre and Mega Groudon spoil the existence of ORAS? Nobody took the Mega Mewtwo twins and the Kanto starters Mega evolutions to mean a new Kanto re-remake was coming, so why would Kyogre and Groudon be different for Hoenn remakes?
Also, if they specifically wanted to keep them secret, why weren't they keeping other things secret, like Hoopa, Diancie, and Volcanion? Or the Megas of the Eon duo? If they were both willing and able to deal with a mid-generation patch to add in Megas from ORAS, there's absolutely no reason they couldn't do the same for the above-mentioned Pokemon.
Many trademarks never amount to anything.
And simply pointing out that they look different in no way points specifically to Mega Evolution. It could be a Mega Evolution, a new form, or, hell, maybe Team Magma / Aqua enlisted the help of Cipher and they're XD002 and XD003. It could literally be anything.