I would guess the answer to that question is "Never." What China is good at is manufacturing anything that can be simplified, automated, and scaled up. An optical rangefinder is exactly the opposite of that: it's complicated, has to be adjusted at least partly by hand, and isn't in high-volume demand.
On the other hand, they might come up with a different approach. Suppose somebody came up with a "range/viewfinder" in which the viewfinder consisted of a phone-size camera, and the rangefinder consisted of a second camera, offset from the first to provide the moving image, plus electronics to combine both images in an EVF. A digital micrometer would read the coupling cam on the back of an M lens, providing the input for adjusting the moving image. There would be no moving parts at all except for the micrometer. All the initial setup could be done on an automated rig, and any subsequent alignments could be done by the user without tools. The EVF also could be used for viewing the sensor image conventionally, or for reviewing images taken. In other words, a conventional mirrorless camera with EVF, plus an add-on range/viewfinder module and micrometer.
The looming question would be how many people would pay extra for the added parts compared to the cost of the base EVF mirrorless camera. Not many, I'd guess. Except for the Yi M1, China doesn't seem to have jumped into the camera-making business in a big way except as a manufacturing site for existing companies, so I suspect they don't see this as a business with a lot of upside.