To me that defies reason, science and engineering. Any technology only improves and becomes more scalable. The Chinese are building a gigantic dam with 3D printing and no human intervention. While I agree 3D printing is not there yet for rapid mass production there is absolutely nothing impossible about achieving it. And after that will come nanotechnology assembly or biologic assembly. The current stamp, mold and weld workflow will be replaced entirely within Musk's lifetime and he might even have something to do with it knowing him.