Mega Evolutions of Sceptile, Swampert, Groudon, Kyogre and Rayquaza don't even exist in the coding of Pokémon X and Y. This can be proven by using a 3DS save editor code with the offset of where the items are saved, hex value of the item slot and the hex value of the item you'd wish to use to replace the item in that slot. You'll find there's no Sceptilite, Swampertite, Groudonite, Kyogrite or Rayquazite in there. However, that doesn't rule out that there won't be any new mega evolutions in the game. It's definitely possible, even without requiring a patch to X and Y. Pokémon with new mega evolutions battling in a game that doesn't have the models of those mega evolutions can still appear in battle in their regular forme, rather than mega evolution forme. Just like as it was with Black Kyurem in Pokémon Black Version 2 battling against a player playing Pokémon Black Version, or even Giratina's Origin forme in Pokémon Platinum Version against a player playing Pokémon Diamond Version.