Id Software actually finished Doom 3 and sent it to the print. It will be available around the world starting from 5th of August this year (less then 3 weeks left). Slashdot story on the announcement is here.
There also an updated story here, which links to the blog entry of Todd Hollenshead of Id fame.
Doom people should run as fast they can into hardware shops to upgrade their PCs. I myself will wait for Quake IV. :)