Two words: net boot. I can envision a scenario where, among the various diversifications of computers (desktop, laptop, netbook), one class becomes pure internet terminals. They have no hard drives at all, and instead boot straight from the net.

Naturally, this would require a massive upgrade of the existing network infrastructure, including true gigabit ethernet piped directly into our homes. Using the existing coaxial cable infrastructure has been a useful hack, but we’re reaching the limits of that technology, since the “last mile” of the internet is becoming a crippling bottleneck.

But it could happen in principle. It would be useful on two fronts: 1) computers (at least the internet terminal variety) would be cheaper, allowing more people to have internet access, 2) booting the same OS from a central server would allow you to work in the same environment on any computer without the need for back up / synchronization tools.

Of course, my preference would be Linux, but even proprietary operating systems could create a model where booting from a central server to multiple computers would be cheaper than installing copies of the operating system on each one.

Naturally there are security risks, but there are plenty of security risks already. SSL encryption and key identification would be necessary.

Ultimately, users could choose the model that suits them. So get ready for Ubuntu Netboot!

To clarify something:

OS will never become irrelevant, they will only be irrelevant to “average joe/mary” who just wants to get on the Web and work on the cloud.

their are other aspects to an OS: a programming environment (could also be cloud based), a gaming platform (could also be cloud based: internet gaming), etc

well using web apps offline and something like adobe air are also great.

anyway, marketshare and mindshare will always be big factors