Lately, I've been thinking a lot about the future of the desktop operating system. As a Linux user and a vocal advocate of Linux and free software in general, this is something I think about anyway. I find myself a little frustrated that people waste money on expensive proprietary software when they could be using free software instead (in both the free speech and free beer sense). In particular, I have something of a bee in my bonnet about schools using this - why should my taxes, or Tesco vouchers for schools, go to pay Microsoft when they could be using Edubuntu instead? OpenOffice is a more than adequate replacement for MS Office (and don't give me that about "they need to learn the industry standard", it's just a word processor, I used other ones when I was a kid and I can use MS Office just fine).
I do think there is a change coming. Having been using Linux for a year now, I know very well that distros like Ubuntu are more than ready for the average Joe. Anyone who thinks that Ubuntu is hard to install must have not installed Windows XP (which is a lot harder to install than Ubuntu). It's just the fact that you have to install it at all that fazes some people, and the fact there are differences between that and Windows. If you were buying your first computer and you got it with Ubuntu preinstalled, it wouldn't be any harder to learn to use it than Windows - in fact it's easier in many ways.
I know several people who don't consider themselves Linux users, but own an Eee PC, and use it without any problems at all. This device, in particular, has made it clear that a well thought out Linux distribution can work for non-technical users.
Add to the fact that Windows Vista is getting a reaction somewhere between lukewarm and outright hostile, depending on who you ask, and it makes me feel that a shakeup on the desktop is imminent. Microsoft are pressing ahead with plans to withdraw XP from sale, but vendors such as Dell and HP are exploiting loopholes to keep selling it.
I do keep hearing rumours that Windows 7 will see major changes to Windows, similar to what Apple did when they moved to a Unix base. There are suggestions that the whole OS might be rewritten from the ground up, getting rid of much of the bloatware. It's difficult to tell what impact this might have. On the one hand, these changes could save Windows, fixing major problems with the operating system and improving performance no end. On the other, changes of this magnitude would very likely break compatibility with previous versions of Windows, so people couldn't use their old software, although I can see how they could include some kind of virtualization software to get round this. Also, people don't generally like the changes in Windows Vista, so more radical changes might go down like a ton of bricks.
Apple, of course, will remain a part of the desktop computing scene, but the fact is OS X is not going to grab a majority market share any time soon. The only way this would happen is if Apple were to license OS X to other hardware manufacturers, which I can't see them doing any time soon. Also, if Apple did somehow wind up pushing every other hardware manufacturer out of the market it would be worse than Microsoft's current near-monopoly - they'd control both the hardware and software markets, which is worse than Microsoft controlling just the software. Sorry Mac fans, but never going to happen, not while there are industry regulators around! Apple's market share may well increase, but they aren't going to take over the world, fact.
If other OEM's start losing significant market share to Apple because Windows became a liability, you can bet your life that they will start looking around for an alternative, and Linux is the most likely choice (but not the only one - it's possible that other desktop operating systems such as FreeBSD might also benefit).
One thing to note is that if something like this happens, growth in Linux adoption is likely to be exponential. For instance, greater numbers of Linux users means that more hardware and software manufacturers will support it, reducing the problems people have when switching so that more use it, creating a reinforcing loop. While I don't think Linux is likely to wipe out Windows any time soon, if at all, it could easily become much more significant than it is now in a very short space of time.
I actually think that if it was better supported by games manufacturers, Linux would be a better choice of operating system for hardcore gamers. These are the people who will spend lots of time and money building a custom gaming rig that's designed to get the absolute best performance possible out of their computer. To me, it seems a bit of a waste to then have a bog-standard Windows install on it. I'm sure many of these people would really appreciate being able to use a distribution like Gentoo to compile the whole installation from scratch and customise it to get the very best from their computer. For people like this, the desktop of choice may be much less important, so they could use a window manager like IceWM or Fluxbox, meaning they can then save the processing power for where they really need it. Something like Aero is a waste of processing time if you're looking for gaming performance.
Whatever happens, I think the next few years are likely to be interesting. One thing to note, though, even if you're happy with Windows or OS X, is that any growth in Linux adoption benefits you as a consumer, even if you don't use it. I'm not just saying this as a proponent of Linux, but if Microsoft and Apple have more effective competition in the desktop operating system market, they will be forced to improve their own products to compete. The nature of Linux, with hundreds of distributions competing with each other, means that it has improved in leaps and bounds over the last few years, and will no doubt continue to do so. The entry of Linux into the mainstream desktop market would really shake up the scene.
Anyway, that's just my thoughts, and you may disagree - please feel free to comment!