Here's a contrarian idea: Microsoft ignores its critics and doubles down on the Modern UI. Via generous financial incentives, Microsoft sways developers to stock the Windows Store with plenty of multi-touch apps, thereby making the Windows 8/RT platform a worthy competitor to iOS and Android. Future versions of Windows do away with the desktop entirely. And enterprises don't mind because Microsoft continues to support and upgrade Windows 7, which they prefer anyway.
This scenario has serious flaws, most notably the fact that it undercuts Microsoft's unified-interface strategy for Windows PCs, tablets and smartphones. And it would make lots of long-time Windows users very, very angry.