Unless game and app companies adopt a new OS to release on, I don't see windows as being dead.
The subscription model is something that is going to be part of the future. This was discussed year ago, that eventually Windows will be subscription based and / or the windows update component.
It makes sense since Windows 10 is the last version (allegedly) and that any future changes will be delivered through updates, it is only logical that they would add subscription policies to it as eventually they still have to continue generating revenues.
For a company, subscription based is not much of an issue as some are already subscribed to some product or service of some kind.
But this will eventually happen on consumer editions, not for now, but I can see this happening few years down the road, and not only for Windows software. Perhaps as a measure to control piracy, one day parts of the software code would be available online and only unlocked upon subscription requiring being always online and connected to use the software, though nothing is impossible to bypass (remember what they said about BluRay protection
)
So perhaps they will say ok, consumers pay a monthly fee OR can opt out of it and allow us to add ads and monetise your OS
In any case MSFT revenues is not primarily from consumer Windows users, so I think that perhaps they might add fee based services or subscription based services to parts of the OS, not the Windows itself but components - There is lots of piracy in the consumer world and game companies have learned that adding draconian DRM to their titles does not make things better, it makes the opposite happen, so unless Microsoft wants to see an increase in piracy or completely kill the consumer market for windows, they would be on the right path to do so - but subscription model and cloud based seems to be the future, and many software companies are going down that road, so you can bet that Microsoft will follow - why wouldn't they if others are doing it............