Beer drinking Australian futurists Tristan Grace and Nathan Waters speculate about the future of 3D printing on their podcast, episode 24. They feel that the ultimate goal of 3D printing is in fact very small: nanotechnology. In other words, that's printing individual atoms and molecules in the right arrangements to achieve virtually any conceivable object.
They say that right now we're "watching 3D printers grow like we watched computers grow when were kids". Today they print plastic, stainless steel, but how long until we print circuits? Once that happens, consumer goods become possible. They propose "printing an iPad", but realize that by the time they could do that, the iPad will be considered "quaint".
They foresee 3D printers with ever increasing resolution, theoretically all the way to atoms: "molecules will be the biggest thing". Of course, they realize there will be very significant societal implications that are difficult to predict.
Best idea: Eventually "physical objects become software, and that's when the Internet really joins everything." Then the atomic economy meets the software economy.
Via Vimeo (start around 13 mins in)