Oh, I agree that 3D printing will be a serious threat to manufacturing as we know it. But not at home. That doesn’t make sense. Instead, we’ll have two kinds of communal 3D printer shops.
In high-infrastructure areas, there’ll be a clutch of online providers a la Stratasys (and I expect one of them to be Amazon.com): you’ll pick your 3D design from a huge online menu, send them size information and maybe a few photos from some kind of cunningly designed app, tweak the 3D preview until you’re happy, and they’ll print it out in some vast warehouse full of high-end high-speed 3D printers and ship it to you, possibly that same day.
In low-infrastructure areas, or if you’re a casual hobbyist, or if you have very specific requirements, you’ll head down the road to your nearest local printing facility. Depending on where you are, maybe this is tomorrow’s TechShop, maybe it’s a cluster of converted shipping containers on the outskirts of Uganda each with their own specialties and strengths. They’ll customize your order, render it in the cloud as needed, print it out, and tweak and iterate until it’s done. More expensive but more specific.