From the comments section of an article in the Torygraph which expresses scepticism about 3D printing:

“My company has recently acquired a 3D plastics printer for £26K and it’s slashing the time it takes to make components for automated machine builds from weeks to hours. Admittedly the components are used in less critical areas and yes the materials are limited. But in 15-20 years time the material variety and precision will be addressed. It will never replace high volume manufacturing, but for small scale/volume engineering it could become the mainstay. Metal 3D printing is also well established.”

All sorts of materials can now be used for 3D printing: rubber, silicone, food, etc. I’d say that material variety and precision will be addressed sooner than the commenter thinks.