I see this as the continuation of the slow death of Windows. In my opinion, Windows 8 is a frankenstein of an OS with the Metro UI bolted onto Windows 7 without a start menu, that’s confusing for the average user. Also, as I previously mentioned, the WindowsRT story isn’t compelling.
At the high end, people are migrating to Apple Macs that work better with their iPhones. Everyone else is happy with less inexpensive Nexus, Amazon (and low end iPad) tablets and the PC just gets used when there’s a need to run a particular app.
This can only mean an increased potential for mobile apps. As people try to do more on tablets we will probably see more sophisticated apps developed that do a lot more than the average $99 app. There’s currently a land-grab opportunity for developers to create apps that can displace those used on the PC… if they can convince users to pay for them.