I have just updated to Windows 10 from my 8.1 and can report that both WotLK and Cata (assuming MoP as well but haven't tested) are fully supported and not crashing or getting banned by the hack protection.
One issue I have found on both clients however, is sound... it automatically sets output device to system default.
This may be limited to laptops but for all you playing on desktops it would be still worth checking it out just in case.
