I certainly wouldn't go so far as to bet that Windows will go away, but I think that previous predictions about Windows demise were predicated on it being replaced on people's PC's with something else.

That never happened (and I agree may not ever happen), but I think the growing widespread adoption of non-pc computing devices (phones, tablets, tv's, etc.) definitely has a fighting chance. Within ten years, I'd bet that the vast number of people will be accessing the internet primarilly from something besides a PC.

Everyone was thinking years ago that no one could displace IE as the dominant browser - that Microsoft could and would pull every dirty trick in the book to kneecap the competition and outcompete with mass developers.

Now look - Firefox is sitting comfy, Chrome is a rising star, and on mobile, webkit browsers owns the whole place.

Windows can and will fall. If Microsoft is smart, they'll be the ones that put it to rest (like Apple had the mock funeral for OS9) on their own terms.

The difference is that with a web browser, you can switch from IE to a superior browser and all your favorite web sites will still work (apps built for IE6 compatibility notwithstanding). This isn't true of switching from x86 Windows to some-other-OS on some-other-architecture -- your existing special-purpose business apps won't work. You have to switch everything out.

That's not to say that Windows can't get displaced, but that it's a lot different from displacing IE. You can't just switch from Windows and have nearly everything working the same from day 1.

Most applications aren't speed critical, so on some-other-OS on some-other-architecture you'd probably get away with virtualization / emulation.