I think easily within 50 years, probably more like 30. Having said this I am one of those people who follow Ray Kurzweil and believe that we may have some sort of technological singularity occur within the next 30 years or so. If that does happen it is virtually impossible to predict where 3D printing will fit into all of this. There is no doubt that within the next 15 years we will see some of the most incredible advances in robotics, 3d printing, nanotechnology, materials science, intelligent computers, genetics and healthcare we have ever seen. I am willing to bet that the progress we make from now until 2030 will be more than that which was made from 1960 until today.