40 is too low, the absolute bare minimum will be about half the Wii sales, or 50 mil. But IMO it will exceed 70.mil. Gone are the uncool purple hot mess of a preschool lunchbox GC days (though a darling to us hardcore), Nintendo consoles now fit in your living rooms w/o shame. It is a mainstream monster, and the "Wii fit" series alone will keep it strong combined with the hardcore & new fans gained. Obviously, I am playing to the loud minority by saying it will lose 30 mil (100 mil Wii sold to 70 Wii U) so even 70 mil is still a fairly conservative estimate.
Make no mistake, being a new product, virtually all alone (ps360 market is saturated + have "old" reputation) & guaranteed to be the most affordable yet again, should leave Ninty on top of the throne again. Microsoft cannibalized Sony's market and that trend will continue, but X8ox will be a $premium$ offering that will always be in 2nd place, like Sony handhelds.