Pete Travis is scheduled to direct the $50 million movie this fall, so they do need to start casting soon - and Urban definitely has the build and acting chops to play the gritty anti-hero.
According to Bleeding Cool, one major contract provision is that Dredd will not take off his helmet - the entire film. Considering Urban isn't a huge star, though he's been in plenty of huge franchises, there's a good chance he'll be fine playing a helmeted-Dredd (unlike the 1995 Sylvester Stallone film).
Though Urban will be offered the role, it's unknown whether he'll take it. His duties as Bones McCoy in the Star Trek sequel may just take him out of the running. Trek 2 which will be filming next summer, if producer Bryan Burk is to be believed. However, a summer Trek shoot might be perfect for Judge Dredd with Urban.
The Play List recently reviewed the Judge Dredd script, penned by 28 Days Later writer Alex Garland, and said the film sounded like a "vertical 16 Blocks" or "Die Hard taking place within the world of Blade Runner." While the script isn't perfect, it succeeds in one of the most important aspects of any good Dredd story - its gritty and violent.
Will Urban take the role if his schedule permits? In my opinion, he'd be crazy if he passes. The Judge Dredd reboot could provide Urban with his own headline franchise (something that Star Trek isn't).
We'll have more on Judge Dredd as we get it.
Sources: Bleeding Cool