[Yetanfou]

The lower levels of Windows 10 are probably the least problematic so basing a 'new, clean, robust OS' on OpenBSD (which, by the way, Apple did not do, they used parts of the FreeBSD userland on top of a Mach-inspired kernel) would not do much good as they'd still have to include support for Win32 for it to be considered a replacement for Windows. It is there Windows really shows what it is made of: glue, tape, rubber bands, hastily erected scaffolding around sassing facades, heavy structures built on top of unstable foundations. Microsoft tries (and tries, and tries) to replace all that with something new but they have a hard time making up their mind what the replacement should be and where the focus should lie.

In this sense a good successor to Windows would be a lightweight VM host running one-off instances of older Windows versions to support the host of software made for that platform, allowing those instances to communicate with each other. That might be good for users but it does not offer a path forward for Microsoft.

In truth, there probably is no way forward for Microsoft in this space. Windows is a dead end, the 'information at your fingertips' idea which Gates spouted has come true but not by way of Windows.