The newest installment of Conventional Computer Wisdom holds that Windows 7 will be "a Linux-killer," unseating Linux on netbooks and sealing its fate on the desktop. Well, maybe XP-killer and Vista-killer is more like it.
The details (as mused over at ComputerWorld.com) go something like this. Linux is taking off most aggressively on netbooks and similar devices. Windows 7 was designed to run well on such machines. Therefore, once Windows 7 is out, Linux market share on those devices (and, by the same token, Linux market share in general) will implode. It sounds fine in theory, but the picture has pieces missing.
1. Netbooks are not the only place where Linux is finding a foothold. Smartphones (hello, Android!), embedded devices, kiosks / corporate desktop setups ... not all of this is as sexy or attention-getting as the desktop, but it's every bit as crucial.
2. The ways in which people are explicitly dependent on Windows is decreasing. While I don't think the Web is going to completely replace desktop applications anytime soon, it's already happened for many people whose needs are relatively undemanding. Each new generation of PC users that comes along starts with a clean slate, and are that much more likely to start with Web-based apps rather than a Microsoft product that requires a Microsoft platform.
3. Microsoft competes most directly with itself. Been said before, but it bears repeating. By and large, when people shirked Vista, it was in favor of XP or holding out for 7 -- not jumping ship entirely for Linux. Forums and blogs (like this one) are peppered with no end of anecdotes from people who shirk Windows in favor of some grade of Linux and never look back, but I don't expect that to become the rule rather than the exception. At least not until, as per No. 2 above, a generation of computer users comes in who have no particular dependence on Microsoft to begin with. We're well on the way, though.
So what'll happen with 7? I see Windows still keeping a majority slice of the desktop pie, with Apple and Linux splitting the difference. The size of that difference is certain to grow, but it's going to continue to be a Windows world for the most part.
That said, I've long been of the opinion that Linux doesn't need to "steal" market share from Microsoft. Not for the sake of its own survival or development, certainly. It does make sense for Linux to stay feature-competitive with Windows in the sense of hardware support, something that's far less of an issue now than it used to be. But Linux will win, and has won, its own audience in its own way. It's never done any less than that.