Duke Nukem Forever's official website recently linked over to preorder pages on Amazon and Gamestop, and both say the game is due for release on Feb. 1, 2011.
The most recent information had Duke Nukem Forever releasing in early 2011. Feb. 1, 2011 is a Tuesday, the traditional release day for video games in North America; it is not the end of a financial quarter. It may be a placeholder date. I've emailed a Gearbox contact to ask for further comment.
Update: A Gearbox representative says any date out there is a placeholder only.
Duke Nukem Forever [Site]