Actually, look at the tests. The gun costs $25 to make on a 3d printer and it's deadly accurate. Of course there's the issue of reliability as these guns explode easily and unpredictably but these tests were done 6 months after the prints were made available. Why shouldn't we believe this will be improved upon if this much progress has been made in the first 6 months?
http://www.forbes.com/sites/andygree...xplodes-video/
Also, the government is very much staying on top of this as it is escalating. See what's happening with the dude who made the Liberator and his connection with bitcoins.
Also, the British Air Force is already using 3D printed parts on their fighter jets.
Wanna predict 2 years into the future on this technology?