Welcome to the forums :)
From the top of my mind, the things which you have slightly wrong in your analysis are:
1- production at 1.8 million per month started from around July June, not September
2- according to Nintendo, it takes 20 days to take Wiis from factories to store shelves (which partly cancels out number 1 ;))
So I'd say supply will be even bigger than you calculated. My prediction for the total number of Wiis sold worldwide by the end of the year is 18.5 - 21 million, depending on demand. Shipped numbers may be around 22 million.
Conclusion - more likely than not, there will be shortages in many places. If it sells out almost everywhere, sales to customers may be even higher than 21 million, so maybe I should have written 18.5 - 22 million!
My Mario Kart Wii friend code: 2707-1866-0957
