You'll see them in home mostly, not garages. Think about the early days of computers taking up an entire room, now they fit in your pocket, and on your wrist (Galaxy Gear, etc). When I think about the future of 3D printers, I visualize "FDM"-type printers using natural filament (or whatever the equivalent will be), with micro-particle ink droplets (think inkjet) being infused in the molten material during printing, for full color prints. Size probably won't change, afterall, you'll need it to be the size of the object to print, at minimum. I think we'll continue to see FDM, SLA, SLS alongside one another. Afterall, we have inkjet, laserjet, etc. No one technology needs to replace the other. One might just be preferred for different tasks / outcomes.