Anyone remember Prey?
It started development (as some rough concepts) back in 1995, and wasn't released until November 2006! But, was a success in the end, selling over a million copies.
Prey was a decent FPS, but nothing amazing. I'm glad the game was made, since I'm not sure Portal would have came out if it wasn't for some slight Prey influence, and it didn't really do anything amazing on the tech side, just using iD Tech4 as its engine, but whatever... Prey eventually was released as a pretty polished finished product, that was fun and sold copies.
With something like a Duke Nukem game, I'm not sure how they could screw it up to the point where it wouldn't sell copies. It just seems like the developers have lost direction and don't know how their going to tie things into a finished product. When they eventually do, I actually have confidence it will be a decent and fun product, that will make a lot of money.
I just don't expect anything for a while on this one. If I had to guess, I'd say 4 years (yes, I pulled that out of my bottom)... but, never seems unlikely with so much potential for profit on this IP.