Honestly, i predict people and businesses will keep using Win10 years after it's become unsafe. We've all seen the local warehouse still running Windows 7, i'm thinking that scenario but for millions of users.
That's a cybersecurity problem, but what i'm most concerned with is the e-waste problem, because there's still going to be a lot of users that do replace their PC. There aren't enough Linux users to buy all the computers that will be rendered obsolete, and there won't be by then either. I myself am a new Linux user but i'm already covered, i don't need more computers, not even for cheap.
I just really hope this doesn't end with millions of good computers landfilled or parted. The third world already buys a lot of our e-waste, so i hope they'll get a crapton of relatively good computers for cheap and run either Win10 or Linux