I think vläd is right on the money here, although the sad thing is the timescales involved here. Sadly I doubt nVidia could practically, so soon after the 200 series, release an entirely new design to compete with the 48*0 series until the middle of next year (Q4 this year at the latest).
Personally, though, that's not going to be a problem
Mid '09 was when I was thinking of getting a new desktop anyhow, so I think I shall wait to see what nVidia comes up with and how the market and drivers mature.