The latest Windows 10 update shipped with AF_UNIX socket support for win32 sockets.
It's not that exciting because it doesn't support socketpair() or fd passing - yet. So really it doesn't offer us much more than we can already get with win32 named pipes. We can - and do - already get fd passing with DuplicateHandle anyway.
Still, I thought it was interesting. We could probably just conditionally enable AF_UNIX sockets on new enough windows SDKs. Apparently if it's not supported by the OS runtime you get a graceful error.