MasterofArcanine
Pokecollection Maste
I KNOW that it has never been done before, and I know that there are all sorts of patters and formulas and what have you that people have come up with, but I still don't fully understand why new Pokemon can't be introduced mid gen? I understand as to why previously, but now ..Not so much... I mean, if they are going to have to patch X/Y to include the newly released megas in ORAS, why can't they simply include the new Pokes in the patch as well?
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Well my thoughts on this question comes in 2
1. new Pokemon in the form of new Evolutions for old Pokemon- Sadly I don't think they will be doing these at all anymore expect for maybe new Eeveeolutions. I have a feeling Mega Evolutions will be replace new evolutions for old Pokemon now, though I am hope I am wrong about this.
2. Totally new Pokemon- My guess is that their logic is that Mid Generation (either Remake or 3rd title) is that there is no new region to explore so why have totally new Pokemon. I guess they won't to save them for new regions is why we don't see totally new Pokemon miod generation.
Those are my thoughts as to how to best answer your question.