2011. Developed by Gearbox Software. It's real. I wonder if those people who still have their preorders from 1997 (yes, they exist) are still guaranteed a copy of the game. Also, teaser promo images here. Always bet on Duke.
There's a playable demo at PAX. Kotaku has a writeup. For those who haven't played DN3D, that's basically the last level and final boss of the game. So Duke Forever sounds like it picks up where DN3D left off. Oh, and he has a gold Xbox 360 controller. And strippers.
3D Realms is still around, they just lost the rights to their own game after Take Two sued. I can't imagine how 3DR will be around for much longer, though. The DNF team was fired, and some of them are working at Gearbox to finish the game.