Given the amount of application code that has been written for Win32 over the years and that is still in use, I do not see any viable alternative to Windows on corporate desktops.
Sure, you might have VDI and access a Windows VM remotely from your iPad or whatever, but Windows is not going away for a long time.
(And don't get me wrong, I would love replacing every single Windows desktop at our company with Debian or CentOS or even OSX, but unless a lot of companies decide to port their applications to one of these systems, it is not going to happen.)
Sure, you might have VDI and access a Windows VM remotely from your iPad or whatever, but Windows is not going away for a long time.
(And don't get me wrong, I would love replacing every single Windows desktop at our company with Debian or CentOS or even OSX, but unless a lot of companies decide to port their applications to one of these systems, it is not going to happen.)