As far as the X/Y chromosomes go, I get it...but for now it is just speculation. So I'm not questioning you, or telling you your wrong.
Its just there's nothing stating/hinting that there would be/will be a male counterpart.
I'm sure if that was the case, they'd showcase the male first. I mean the entire eevee line is predominantly male.
If eevee where an even 50/50 split between male/female, then I would agree with your theory.
But seeing as he's not, id have to strongly disagree.
Though I can definatly see this type of evolution happen for a different species.
Maybe one that makes more sense like a Peacock.???