I see a few problems for windows in the IoT realm:
1) Its to heavy. Even the embedded versions need a decent CPU and memory to chug along. Try running Windows on the RPi hardware.
2) Its to heavy. ARM is powering/going to power the IoT since it is so good for lightweight systems and low power usage. Yes, there is Intel Atom, but that series of chips barely makes a dent in the world of connected things.
3) Linux already powers this entire market and development for Linux is cheaper (no Visual Studio licenses) and easier (huge open-source and developer network).
4) Its Windows. Great for businesses, not so good for small, tiny, low power devices.
Far too late. Linux has been free and infinitely more customizable for the "internet of things" since forever