Windows is a desktop OS, and the desktop is dying. In 100 years I’d say the chance of anything running Windows would be about the same as the likelihood of it running VMS.
That being said, I will eventually die. Now, the question becomes what are the people that follow after me going to be using. I have kids in school: both use Chromebooks for school work, in one case a PS4 for gaming, and hand-me-down iPhones/iPhone SEs for social, gaming, and the like. Could they eventually need a PC? Possibly, depending on their career path/interests and the level of support for iPads, Chromebooks, etc. at the time. But they don't need it now. And I know people who are my age and older who limit themselves to iPhones/iPads for technology beyond the TV. None of these things are running Windows.
I'm a developer at work for internal applications (and some external). All of my non-server running things are web applications. They could be accessed by Chromebooks instead of the hp Windows 7 laptops we use now. I doubt we'd switch off PCs due to familiarity at the very least, but we don't need them.
https://www.statista.com/statistics/272595/global-shipments-...
The day of replacing a PC tower every 3 years are gone.
The sales of smartphones on the countries where pre-pay is the way to go are also declining.