Won’t ever happen. I’ve been a Linux developer (SW/HW designer) quite a few years now. The power is Linux is its flexibility. That is what allows it run on virtually any hardware (PC, set-top box, mainframe, server, embedded device like cell-phones and automobiles). Different machines have different functions: your cell phone has very different functions and capabilities than your automotive unit.
IMO, Linux was never really for the desktop/end-user. It’s power is perfectly suited for use in the computing machines users never see: the servers and routers that run the backbone of the Internet, and embedded devices that you never open up or see.
Historically, Linux is a server OS trying to work it's way out to the desktop. Windows is a desktop OS trying to work it's way to the back room.
Poor Linus Torvalds, who moved here all the way from Finland but has recently said quote “I have never, ever cared about really anything but the Linux desktop.” Now he has to sit here and watch Apple eat his lunch.