Nintendo claimed at E3 that Wii was moving toward a 50-50 split of men and women. Historically, consoles/portables were 70-30 splits.
I suspect Wii is going to end up as largely a reconstitution of the NES audience with an infusion of PS2 owners and maybe 20-50m people who never owned a console before.
Final numbers may look something like:
360 - 45m - 20m Xbox owners, 15m PS2 owners, 5m GC owners, 5m people who never owned a console before (either kids or new gamers)
PS3 - 65m - 48m PS2 owners, 5m Xbox owners, 2m GC owners, 10m people who never owned a console before (either kids or new gamers)
Wii - 150m - 67m PS2 owners, 14m GC owners, 1/3 of all PS3 & 360 owners (33m), 36m people who never owned a console before (either kids or new gamers).