Lets see...
1.8 million Wii's per month being manufactured!
1.8x12 = 21.6 million Wii's a year.
Selling like 350k Wii's a week in Jan/Feb = 1.4 mil a month.
That leaves 0.4 million a month to ship extra for big games (hint: Super smash bros, WiiFit, Mario kart Wii).
And considering they don't ship all those 0.4 month they've got left they'll stockpile some of it for the holidays:
(I guess 5 months of 0.4, = 2 millon extra units).
Those 2 million extra units would be for October-December.
And all of that is about a sellthrough of 20+ Wii's in 2008!
So, there ya go: Wii at 40 mil by end of 2008.
THE NETHERLANDS