When can we expect an SMG?
Or something to compete with the AK for "Outlaw's Choice".
It'll take a long time. The first 3D printed "guns" were simply lower receivers (the part that's legally considered a gun for an AR-15 build) mated to metal parts for the rest. And they were chambered in .22LR, one of the lowest powered commercially available rounds. Plastic is still limited in its tolerance for heat (especially from friction) and the sheer force of firing a load of smokeless powder. There's a video on Youtube of a 5.56mm printed receiver being used, and it repeatedly malfunctioned before finally separating both halves in his hands.
Printing an entire gun is only practical for a criminal who only needs a few shots in its lifetime, or never even intends to fire it and just wants to use it as a threat that's more useful in an emergency than a $5 springer airsoft pistol. The gun won't last long before it's no longer serviceable. And 3D printers still aren't exactly cheap, so you'd probably be better off simply buying a regular gun from one of the countless black market dealers. The days of the Mafia having massive 3D printing shops making assault rifles, or a poor thug printing up a submachine gun in Compton, are still pretty far ahead.