My thoughts on the whole DNF thing.
DNF became gaming's equivalent of GnR's Chinese Democracy. I do admire their quest for perfection.
I do think they're keeping hush hush about the engine for a reason. I don't think the screenshots look bad though. Any game in development for this long with this attention to detail is going to impress regardless of the game engine used.
I would love for them to finish the game and finally see it released. Then do a GOTY edition where they package the finished game with all the different engine builds before it "as is"... meaning you get to play wherever they were at in 1998, 2001, etc, these would be unfinished of course but playable. Throw in a DVD documentary and level editor. Although I'm not sure Gearbox would want it known how much they did or didn't truly add to the game (who cares, I say, they're the ones who made it happen).
I do think the game will easily eclipse the past Duke games which imo haven't aged as well as other FPS games.
I will still laugh my tail off if it gets delayed.