Given that Raven won't have to pour the majority of their effort into developing the game engine, I think they'll produce a decent product in time. There is certainly enough time to develop content. Remember it is not just Raven who is doing the work. LEC are also putting in effort.
The wait has been long, and Q3 tech should do fine, even early next year. Given that JKO will feature those high polycount models, and that some gamers will have pretty high-end rigs by then, I think JKO will look and play great.
Sure, Doom 3 tech will blow Q3 tech away, but then again, the dated look of Jedi Knight (even by 1997 standards) didn't ruin that game.
Never give in--never, never, never, never, in nothing great or small, large or petty, never give in except to convictions of honour and good sense. Never yield to force; never yield to the apparently overwhelming might of the enemy.
Winston Churchill, 1941.