Too much fragmenting in their line. Windows RT, Windows 8, now another Windows tablet that's just a game machine? Makes no sense.
What is new about this?
Microsoft Windows has always been a dynamic system. Over the years Windows (NT OS) has run on x86, x64, Itanium, PowerPC, DEC Alpha, MIPS and now ARM. Also, Microsoft has released multiple editions of Windows since Windows 3.11 for Workgroups. Windows NT Workstation, Windows Server, Windows Embedded, Windows RT, Windows Storage Server.
The strategy seems to have worked out pretty well for them.