I am rather sure that X/Y breed Pokémon that get transferred over to ORAS will be able to be used in the new format. Those Pokémon do fall under the "breed in" category with a mark, and more then likely ORAS will require the game symbol (if the games continue the symbol and they do opt to keep X/Y blue symbol)-
I do not see much of an issue to not want to start breeding for the transfer over.
I think the entire reason to have those symbols was a way to track a better history of a Pokemon's "history" and to be "filtered out" of the older system to in hopes of having a non-hacked atmosphere all- around.
Even though it is electronics, and hacks are still around- the best thing to happen is the attempts to weed out the hacked and try to implement a better system to conquer a never ending cycle (but to greatly slow down the process of allowing hacks to get into the competition which is the #1 main concern of the players base IS handling hacked Pokies in battles)- so, over all- I think we can see a rather smoother transition to making the jump to ORAS with less hassle.
For example- there should be a compatible way to link the Bank between X/Y to ORAS, and, Bank is a filter as it is- and to me it looks as if people are welcoming the attempts to make the competitive scene "hack free"- there shouldn't be a step back but steps forward to move on to include the combination of X/Y and ORAS to better the games for everyone.
My guess as well that there will be some point in the new games that Bank will not be accessible right away (if so, full dex right off,
), but, to be X/Y mixed per say to have access to all the POkies is looking like the format will be expanded into a lager base to break up the meta in allowing more available Pokémon to battle.
If they do decide to restrict the format to ORAS for the format and restrict the Pokémon to that dex only- I think there will be a great amount of severe disappointment and a huge step back and IMO it will hurt the game. As I see it, instead of restricting the stratagies to only a select few battle worthy Pokémon to a format is most hurtful and creates a format that is left to a "stale year" of seeing the same teams face off due to the lack of strategy out there when there are so many battle worthy Pokémon and so many teams to create- it would be great to see different teams throughout the year then just what is "meta" the whole year and being predictable and repetitive.
my thoughts, 2 coppers is all--