^Rest assured, any additions of Megas to "XY2" were probably planned out years ago, just like the addition of new megas to ORAS was well-known when XY was in development. Ccase in point - Mega Blaziken being an event download for XY at launch. No way GameFreak would ever implement a Mega Blaziken without having planned for a Mega Sceptile and Swampert too.
Masuda (?) once said in an interview that the Mega Kanto starters were added to XY once he saw the designs in action. It sounds like they weren't meant to be available originally, but were added quite late in development (whether or not he meant "available during the story" or "available at all" is open to interpretation, but I assume the former). My little pet theory goes that the launch event was originally scheduled to be a Charmander holding the Charizardite Y (under a different name), and that originally there was only one Mega for each Kanto Starter. Due to its heavy exposure in Origins, I presume Mega Charizard X was the "original" Charizard Mega Evolution, whereas what we today know as Megazard Y would be some sort of bonus. However, with the inclusion of the Kanto starters in the story, the event had to be rescheduled at a point late in development, so the already-designed Mega Blaziken was implemented in XY and Torchic given out as an event instead.
That, or the Eon Duo were originally scheduled for the launch event, but scrapped either due to blatant overpoweredness or because their Megas were too similar to highlight a version difference. Either way, I remain rather convinced that the implementation of Mega Blaziken in XY was due to a change of plans, but that the entire Hoenn Starter Mega trio were designed, with the relevant code ready long before XY shipped.
Anyway, whatever the reasons for not patching XY were, "they hadn't planned for it" is not among them. Whether or not ORAS will be patched when "XY2" comes out remains to be seen, but I'm leaning heavily to the "no" side.
Masuda (?) once said in an interview that the Mega Kanto starters were added to XY once he saw the designs in action. It sounds like they weren't meant to be available originally, but were added quite late in development (whether or not he meant "available during the story" or "available at all" is open to interpretation, but I assume the former). My little pet theory goes that the launch event was originally scheduled to be a Charmander holding the Charizardite Y (under a different name), and that originally there was only one Mega for each Kanto Starter. Due to its heavy exposure in Origins, I presume Mega Charizard X was the "original" Charizard Mega Evolution, whereas what we today know as Megazard Y would be some sort of bonus. However, with the inclusion of the Kanto starters in the story, the event had to be rescheduled at a point late in development, so the already-designed Mega Blaziken was implemented in XY and Torchic given out as an event instead.
That, or the Eon Duo were originally scheduled for the launch event, but scrapped either due to blatant overpoweredness or because their Megas were too similar to highlight a version difference. Either way, I remain rather convinced that the implementation of Mega Blaziken in XY was due to a change of plans, but that the entire Hoenn Starter Mega trio were designed, with the relevant code ready long before XY shipped.
Anyway, whatever the reasons for not patching XY were, "they hadn't planned for it" is not among them. Whether or not ORAS will be patched when "XY2" comes out remains to be seen, but I'm leaning heavily to the "no" side.