Obviously, we do not have self-replicating machines at our current level of technology.
Advancements in AI and fabricating technology (example: 3-D Printing) could change that within the next hundred years.
I’m not the originator of this idea; in fact it’s been kicking around among scientists and engineers since the 1940’s. There is even a colloquial term for one hypothetical class of self-replicating machines: they’re known as Von Neumann machines.
I expect AI to grow to the point where it can replace engineering labor (e.g. set performance goals and develop engineering designs for machines to attain them). Whether you will define this as autonomous or not depends on the human level of involvement, which is a design option rather than a necessity at this imagined level of technology.
We can imagine it because it’s really not all that far beyond what we can already do.
It’s fine if you prefer not to join me in imagining a future technology. But it’s probably wise not to say ‘this is how we do it now, and this is how we’ll always have to do it.’