Nintendo has (sort of) announced the release date and price of the Wii. In typical Nintendo style, they were a bit vague about their plans, still refusing to nail down the details.
In part, the reason for this has to do with the way this news has gotten out: Nintendo has released a fiscal year 2006 (FY2006) projection for investors (corporate fiscal years tend to begin and end in July), and in that projection report they make statements about how they will handle the Wii launch.
According to Nintendo's figures, the Wii will indeed launch in the Fall of 2006. Gamers have been aware of this for quite some time, and Nintendo still has not nailed down a specific launch date. However, they have stated that the Wii price tag will not exceed $250 in America, or ¥25,000 in Japan.
Regarding the quantity of Wii units that will be available at launch, Nintendo stated they would ship six million units between the launch day and March 31, 2007-- a time period officially described as the "launch window".
The launch will be a worldwide event, so these initial six million units will be distributed around the globe. In total, Nintendo expects to ship 17 million Wii units worldwide in FY2006.
Nintendo added that announcements about the specific launch date and exact price of the console will be made "soon."