While I personally don't think 2010 is too early for a new handheld (the DS will be 6 years old) I'm not so sure I believe the rumour ...
For several iterations of hardware, Nintendo has avoided using any component unless there were two manufacturers who could produce the component or unless Nintendo owned the IP or had manufacturing rights to it. The main reasons for this are that Nintendo doesn't want one manufacturer to act as a bottleneck for their system's production, and Nintendo doesn't want to be put in the position where they have to redesign or replace their system because one component doesn't exist anymore; if you look at the past couple of generations of hardware you can see that Nintendo's fears are well founded based on what has happened to their competition.
From my (limited) understanding, nVidia has never been too successful at negotiating with Nintendo primarily because nVidia is very protective of their IP and Nintendo's requirements simply can't be met by them. Now, this could have changed, but I personally wouldn't be betting on it ...
