Corporations will continue using Windows the same way they'll continue using mainframes (at least mainframes are interesting machines). If Dell, HP and Lenovo decide tomorrow to ship all laptops with Fedora by default, very few people will install Windows. Or notice it's a different OS. They'll just think that Windows 12 no longer has ads.

Corporations will continue to corporate. Active Directory is a powerful thing. SharePoint is another dependency that's hard to get rid of, even more so when it becomes the file server where all Office content is stored.