There isn't a release date yet but Nitro Circus promises that it will come out sometime this year. All of the footage has been shot and the crew is currently working on post-production and distribution details.
Nitro Circus writes:
"Expect the impossible, ridiculous, insane, hysterical, and purely awesome! Coming to you in 3D, it will feel like you are riding shotgun with the crew."
Here's the new Nitro Circus 3D trailer.