SPOILERS! Update: Chart of Mostly All New Pokemon in X/Y Leak Thread (Enter at Your Own Risk!)

[Nem]

sc94597 said:

Nem said:

Yes, yes. Its still not dimension orders, its cromossomes. Theres a DNA symbol in the logo. Kyurem wasnt on a Pokemon gray either, he was on black/white 2.

It can be both, of course. I think there being a Z legendary, in the shape of a Z, pretty much confirms a Z version (whether or not it is called that seems irrelevant.) Also there is such a thing as a Z-chromosome. 

http://en.wikipedia.org/wiki/ZW_sex-determination_system

Seems like its not Z but ZW. We can look forward to Pokemon ZW then. :P