The real question here is whether operating systems have been commoditized, and if so, what Microsoft should do about it.

It's certainly true that I can get the windows-on-a-desktop paradigm from Windows (pre-8), OS X, or GNOME or KDE from five years ago. I could probably get the Metro user experience from an especially clever KDE Plasma plugin too.

However, despite free software versions being widely available, we've only seen two windows-on-a-desktop operating systems in wide use, and one of them (OS X) has a very limited install base. This means that the free versions are not equivalent to Windows, as much as I'd like them to be.

I see two reasons for that:

1) Getting the details right is really, really hard. This is especially true when there are a large number of computer users who are used to Windows - I don't think it's impossible to make another OS that they would use, but it would take a huge amount of usability engineering. (This is basically what Ubuntu is trying to do; but that's a side note here.)

2) Application compatibility is really, really important. In other words, even if GUIs are a commodity, the APIs underneath them aren't. This is something that is currently being attacked on two fronts - the Web is providing an alternative, standard API across desktop platforms, and non-Windows mobile devices are forcing developers to use non-Windows APIs. That makes Windows just another incompatible system to weigh the costs and benefits of developing for, rather than the standard which every program must support.

Elop isn't just looking at the explosion of tablets and smartphones, markets where Microsoft doesn't have much marketshare. He's also looking at the fact that the Chromebook has been the best-selling laptop on Amazon for at least a year, if not more. That shows that (2) is no longer enough of an advantage to keep Windows on consumer computing devices. It probably is enough to keep it on business workstations for a while longer, but he's smart enough to know that won't last forever - business IT is becoming increasingly consumerized. (1) is still an advantage, but the Chromebook and tablets both show that people will use a simplified, well-designed interface that's not Windows - hence the move to Metro with Windows 8.

Given all this, what is Microsoft going to do? The operating system cat is out of the bag, and it's probably not going back in. People are going to increasingly expect to bring their own devices into work, and some of those devices are not going to be running Windows. If platforms that don't run Office gain significant marketshare in the business world, then businesses will have to start considering alternatives, and maybe even start using formats that aren't doc and xls.

Thus, Microsoft's next move is clear. It offers Office on all popular platforms, allowing businesses to continue to not think about alternative office software. Apple makes its money from devices, and probably won't even fight if Microsoft does this. Google won't be happy because of Google Docs, but Microsoft has enough legacy support and can offer good enough enterprise management features that they'll still do well in this market.

In the meantime, Microsoft continues working full-tilt on Windows - just because it's no longer dominant doesn't mean that they can't make significant amounts of money from it. My thought would have been to bring the Metro interface to Xbox, although apparently Elop is thinking differently. It might even be true that the Office programs continue to work best on Windows. But whatever happens in the OS market, there's no reason Microsoft can't extend its office software dominance for a while longer.