Or that everyone will be using competing browsers, at which point they have less tying them to Windows. It also doesn't hurt to worry about making Windows a first-class web use and development platform via a decent first-party browser.
I've hated Microsoft as much as the next guy - but I hope they pull it together. Or more like throw it out.
They have the organization and the discipline to do it, but there's too much in Windows as it exists today to fit on current mobile devices effectively. (I could be wrong about that reason, but I'm sure its bloat doesn't help)
At the very least the UI needs a full rebuilding. OSX wasn't adequate for mobile computing either. But I can see Microsoft's idea of having fully compatible environments everywhere as interesting but not feasible. But they sure will continue to try.
The web is a close to a write once run everywhere environment as there is today. (it's not perfect for sure).