Valves latest SteamVR survey shows another drop in Windows Mixed Reality usage in August. From a peak of 11.13% usage is down to 8.24% with biggest growth being with Oculus Rift S which has overtaken WMR at 10.85%.
I should say the Survey is not very scientific and I have never seem the survey on my machine.
Long-term Microsoft fans will have seen the story before. Microsoft launches an exciting new product, it gains some traction and then Microsoft seems to give up and the platform dies a slow death. Maybe Microsoft will surprise up with new devices but I think the focus is on enterprise HoloLens 2.