I wonder which keynote he means. Maybe the Rage premiere at WWDC '07?
Or, given the timing of Doom Resurrection's reveal, it may have been meant to be showcased at WWDC '09 and wasn't.
This. Apple had technical problems at the keynote and was unable to show off DOOM Resurrection.
Btw, some direct Fallout homages are now possible in Rage. (another pretty good interview too).