"After yesterday's announcement that DOOM 3 hit gold status, id Software's CEO Todd Hollenshead updated his .plan once again revealing that, now that DOOM 3 is off for duplication, they have commenced working on a DOOM 3 demo." http://pc.gamespy.com/pc/doom-3/530652p1.html
Written in that article: "....but this probably won't happen until after the game has arrived on U.S. store shelves." I probably will not have a glimpse of the finished product then.