I don't understand why this hope is still prevalent.
3D printers are just another tool in the manufacturing toolbox. The sets of materials and structures printers are made from barely overlap with the sets of materials and structures that the same printers make.
If 3D printers could make themselves, I think they would look a lot more like biological organisms and a lot less like laser copiers.
That said, the Desktop Metal parts I've seen are beautiful.
People think that the only thing standing between them and designing cool new useful things is the final "model of thing -> thing itself" transformation, and that if they just had a magic machine to do this automatically, the rest would be easy.
Much like people think that the only thing standing between them and designing cool new useful software is all that pesky syntax, and that if they had some magic application to turn pictures into software, the rest would be easy.
Even if you can print all the structural portions, there's a big problem printing electrical components e.g. motors, and then an even bigger problem printing control electronics...
Although, I think if they end up able to print robust, ready-to-use metal components with reasonable strength (say strong enough for a bicycle frame), that would be a pretty good leap forward. The base tech of what you can do on a desktop doesn't seem like it would quite get there today though.
I would think the next logical step (after metal printing comes down in price) will be to start printing mixtures of metals and plastics, which would eventually lead to being able to print more complicated things such as motors.
