Yeah it's mostly about assumption since it's difficult to know exactly how long they will be in production.
But with the little fact we have to go on I would say something like this:
Wii: 105 millions (no idea if it will have a chance to reach five more millions in NA)
PS3: 110 millions (if PS2 could go bananaz on it's deathbed(last active years) I am positive that PS3 will too)
X360: 90 millions (I think MS will shut off their production earlier than they claim)








