Businesses take forever and a day to implement anything new (or different), so I don't think they'll switch just like that. Regular folks could go to Apple but the entry barrier is high ($$$). And Linux is amazing, but most normal folks don't even know what it is, and it does take a lot more personal involvement to have a system that works as users intend it to (how to install apps, some apps might not have a native linux app, finding alternatives, etc.). For the regular user I think ChromeOS (in chromebooks) is a much bigger thread to Microsoft than Apple or any of the many Linux distros. In education Chromebooks are already huge and Microsoft is trying to get into that market again with what will be Windows Lite (I think?).