id Software announced today that they officially recommend the NVIDIA GeForce FX series of graphics cards for DOOM 3.
To emphasize the endorsement, a special sticker has been designed for GeForce FX packaging indicating that the product is "Recommended by id Software for DOOM 3."
I couldn't find anything about it on id's site. However, the fact Carmack et al would have taken a final decision regarding this issue could somehow confirm the imminence of a release.
EDIT: There seems to be more information on a page nVIDIA has set up regarding Doom 3.