Based on an industry survey, Nintendo has supposed shipped more than 2 million Wii consoles in Japan alone.

According to Enterbrain, the number of shipped Wii consoles as of April 8th is 2 million and 39,000 units. The top selling Wii game is Wii Sports in Japan.
The Wii is still hard to find, as Nintendo struggles to meet demand for the unique console world-wide.
If you can trust the results from the Yahoo! Wii finder (site), the best chance to find a Wii is still in your local mall. The Wii is a no show at online retailers. See also some Wii offers via Shopping.com.
Via Nikkei.Net (Subscription). More Wii News.