You've missed the Windows as a Service announcements then.... a lot's changed in 14 years.
I read them, and until recently nobody really knew what that meant. Even now, it's vague. Windows as a Service seems focused internally and not externally. Meaning that the OS developers will start using similar processes as the Bing, Skype, and Yammer teams. Which allows them to provide updates based on telemetry and user feedback they receive. Allowing them better data on what's going on under the hood. Kind of like what professional race cars do.
It also has been mentioned that it is for generating revenue based on searches and ads instead of relying on license sales. MSFT determined that revenue from consumer licenses was dropping, so why not make up for that another way. Which is what Google does. Google gets revenues from its ads and search as well as the other services it provides and not by selling the OS.
It's not about subscription type licensing like Office 365. In other words you won't be paying a yearly subscription fee for the OS.
MSFT now has its own line of devices like Apple and is now offering its OS like Google does, and therefore it is trying to take the best both worlds
As far as the OS goes it really doesn't change a whole lot. They will still do major upgrades on an annual basis with minor upgrades and fixes as needed.