I think for 3d printers to become common place, 4 things need to happen, 1. scale, They need to be huge, like basically it is made to fit your garage. 2 resolution, the resolution needs to be hugely improved, like unable to see the lines in a very detailed piece. 3, robotic arms. Would love to 3d print something that needs assembling and then it is built by 2 robot arms using AI. 4. Metal printing, ability to print using both metal and steel extremely quickly, this would basically allow someone to print their own car

I think anything before what I've described, unless you get huge cost savings, people will just by from the shop