cnet may 2008 (from IDC) http://news.cnet.com/8301-13772_3-9948454-52.html
This shows the cumulative sales for each console per year. For example, by 2008 the systems will have 27M, 23M, 42M units sold for Xbox 360, Playstation 3, and Wii respectively. 2009 will have an estimated 33M, 42M, 72M total for the systems.
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See also: Rumors Analyst predictions and forecasts for the Seventh generation of video games...