I am going to ignore most of this because it's just more of the same (even if a fair amount is true) - it's fashionable to dog on ms right now. But declaring that using Windows RT (and by extension the full NT kernel) as a basis for their tablet line was a fatal flaw ignores a whole raft of significant potential benefits to across their whole product line. I was surprised when I found out that they were doing a port…
What is sort of weird is that Microsoft is the only company that is doing this with their own kernel. Everyone else (Google, Apple) have appropriated some other open source technolog for that (NetBSD for OS/X, Linux for Android) as if the kernel somehow wasn't a competitive advantage anymore. I have no idea which approach is "better," this is just an interesting observation and might hint at the values of the compani…
Just consider how many great efforts have crashed in the last 20 years: AmigaOS, GemOS (Atari), OS/2, BeOS, MacOS9, Palm, Symbian, WinCE and others. The ones that are still hanging on don't paint a much brighter picture.
I'm sure there are a few teams out there that would have a good shot, but the daunting task+access to good/free that your staff already has experience with... well.
That said, it's great MS is still at it - heterogenous infrastructure is probably a lot more resistant at a macro scale.