Do you have an actual source for that? (Or is this an assumption on your part?)
Nintendo/ATI announced, a while ago, that they had entered into a new technology partnership, which is obviously going to be Nintendo's next console (what else would it be considering they own the company that made the last 2 Nintendo console GPU's?)
http://www.sharkyextreme.com/news/article.php/2077991
Also the following comment is from Matt Casamassina from IGN in response to an email in IGN Cube's N-Query section:
ATI has been in development with a graphics chip for "GCN 2" for more than a year, it's supposedly coming along very nicely
The full response with that info in is here under the title "GameCube 2":
http://cube.ign.com/mail/2003-06-26.html
I agree, though nVidia and ATI are unquestionably the graphics chip market leaders in the PC space.
Yeah I agree, but I don't think current success in the console space is all important for picking a console GPU maker. Its certainly a plus, but definitely not essential (just look at past console GPU's for proof of that).