Organize for growth. Windows will continue to be a big fountain of money for decades to come, I'm sure, but the desktop market isn't growing. Mobile and Cloud are growing, the MSFT lost the war for Mobile. It has to go all in on Cloud, and it cannot allow Windows turf protection to prevent it from winning the biggest possible slice of that pie.
My feeling is that Windows is still a very important sales driver for their cloud offerings, in particular through volume licensing.