Director Joe Carnahan (Narc, Smokin’ Aces) has posted the following on his site:

So Universal has given us the greenlight to begin the prequel script and done so with great enthusiasm. They were as adamant about NOT doing a prequel as I was about doing one but since the Nigerians NAILED the outline, they all got hipped and jumped at it. If all bodes well, we’ll have a completed script inside 8 weeks and be shooting 10 weeks later.
JC

Previously, Carnahan has said that the direct-to-DVD sequel would be politically topical and would certainly include the Tremor brothers, a trio of Nazi whack-jobs.

Carnahan is scheduled to start filming James Ellroy’s White Jazz with George Clooney in December, so it would have to be a fairly quick shoot.