According to 3DRealms co-founder, George Broussard, Duke Nukem Forever is preparing for launch "...when pigs fly". The 3DRealms executive gave an in depth interview on a game that has a more robust release date, Prey, but did not fail to mention everyone's favorite April's Fool game DNF, giving us some interesting information regarding its progress.
In an interview at 1Up, George Broussard was asked whether his team is still working on Duke Nukem Forever and his reply was ...An ever and ever.
When asked when we can expect the game however he became slightly more serious and after officially announcing the "pigs" schedule, he went on to add:
it's definitely going well now. Things are together; we're in full production. We're basically just pulling all the pieces together and making the game out of it. There's a lot that's finished. All the guns are finished. Most of the creatures are finished. And as I said, we're just basically pulling it all together and trying to make it fun. We've kind of got all these disassociated elements that make up a game, and you put them together and things happen. And then you just tweak it and polish it until it's fun, and that's kind of the phase we're in now, just trying to make something that is really fun to play and interesting.
So there you have it from the horse's mouth, 3DRealms is still working on DNF and they seem to believe that the game is almost into the testing phase. Considering the length of time its developers have been working on DNF, the game may even introduce a new gaming genre; the retro-modern.