Well, I wish I could say it is Linux? But which one? Even excluding the specialized custom build versions of Linux (e.g. computer forensics, firewall, NAS server), there are so damned many of them. It's like every Linuxoid techie wants to get fame without fortune by releasing his own Linux distribution.
My best guess is that the paradigm shift that brings about Microsoft's demise as most popular purveyor of operating systems and office suites will be more radical than just another operating system that uses Intel and AMD CPUs. Maybe the shift is happening already with Ipads, Android phones and other "fondle-slabs" as the on-line British Inquirer calls them. And Microsoft has made its own lame attempt to jump on board with its Windows 8 tablets... Ben Myers