You mean make Eevee and all its evos 50/50? That would be unlikely indeed. For one, if you can transfer Pokemon from Gen V to XY, that would make 37.5% of male Eevee family Pokemon transferred to switch from male to female.
I'm sure they could put in some sort of code that adjust the values of any of them that are traded over. Like, if it's a male under the old ratio, it would alter that Pokemon's value so that it remains male after the transfer. Vice-versa if necessary (or required in the first place.)
R- Official Slowpoketail Vendor Official Mawile of the Pokemon Boards.