I don't think Windows will die, as you put it. I can certainly see its market share being drastically reduced, as we've seen with IE. Computing consumers these days are a bit more savvy to alternatives, and the ones that aren't are drawn in by Apple's shiny gimmickery. But I don't think it will die, simply because of what depends on it.
Games, for example, largely require DirectX, and while it's heartening to see the recent dearth of excellent indie PC games that have gone tri-platform (check out the Humble Bundles), all the big-name stuff is pretty much Windows only, with the odd one getting a Mac port a year down the line. If the death of Windows were the target, then lashings of money would need to be spent beefing up OpenGL and moving onto it. I'd love for that to happen (games on Linux woo), but I don't think it will.