I'm not sure how many people are using WMC under Windows 10, but I thought I would update this thread. In late July, I successfully installed Win 10 on my old Win 7 Home Premium partition and used my Win 8.1 Pro licence key to make sure I got the Win 10 Pro version. Dual boot with Win 8 works fine. I have mainly been using Win 8, but I tinkered with Win 10 on the weekends.
I used the alternate branch of the WMC installer (version 8.8.1
by user T-S.) following the readme instructions. Then I ran Peter Near's fix to turn on the ATSC flag for Canada. IMPORTANT - Peter Near's BAT file doesn't work if you "Run as Administrator" - just click it to run. I set up my Canadian postal code and my dual tuner Hauppauge 2250 works fine for OTA and the guide works. Note: I downloaded and installed the latest drivers from the manufacturer before installing WMC, just to be on the safe side.
I installed the Win 10 Anniversary Update on Monday and one bonus is that the 5.1 audio now works in WMC. Previously, it was just playing stereo.
It appears that the Anniversary Update unintentionally broke the ability of U.S. CableCARD users to record protected content like HBO. Microsoft seems to be changing the way they handle DRM in Win 10 and since WMC isn't being maintained, the PlayReady module no longer works for protected content. This doesn't affect Canadian OTA users since we couldn't do that anyway.
I still plan to keep the Win 8.1 partition as a hot backup in case something happens to WMC in Win 10 in the future.