In respond to the opening thread, according to Microsoft Windows executive Jerry Nixon Windows 10 will be the last since the business model is changing. My understanding is that Winows 10 is not only an operating system but a "service" which means that their focus is delivering frequent updates to Windows 10. For more info on the topic I would encourage the following read:
In other words, according to Tech Radar "Microsoft says that Windows 10 will be its final release of the iconic operating system that's installed on over 90% of computers."