It doesn’t matter what’s “removed from their servers”. For people claiming: “well we’ll just download the FOD and install it offline”, this isn’t going to work.
Here is a simplified diagram of what makes WMR:
The stuff in ORANGE is things you can download, the SteamVR/OpenXR packages, the “shell” (Portal) and the device drivers. The critical part is what’s in the DOTTED LINES. If/when Microsoft removes those (and I have 0 insight on that, I haven’t been with that team for >1 year), everything else becomes useless.
These things in the dotted lines are the components that are expensive to maintain (even when no changes/improvements are done to them), so it’s likely they are the things they want to get rid of in the future.
The OS Components are a black box, so it’s not like someone can just go and replace it with their own. Re-implementing the Public APIs would be unnecessarily complex and tedious vs just re-writing something or using Monado (assuming the EDID limitation can be bypassed one day). And there is no public documentation of the driver APIs AFAICT.
By the time all of this is tied back together, your cables will have died anyway. Your headset is working today regardless of the deprecation, just enjoy that.