The standard lighting model in DOOM, with all features enabled, but no custom shaders, takes five passes on a GF1/2 or Radeon, either two or three passes on a GF3, and should be possible in a clear + single pass on ATI's new part.
It is still unclear how the total performance picture will look.
Lots of pixels are still rendered with no textures at all (stencil shadows), or only a single texture (blended effects), so the pass advantage will only show up on some subset of all the drawing.
If ATI doesn't do as good of a job with the memory interface, or doesn't get the clock rate up as high as NVidia, they will still lose.
...
I fully expect the next generation engine after the current DOOM engine will be targeted at the properly general purpose graphics processors that I have been pushing towards over the last several years.