It's worth keeping in mind that there's a countervailing trend though. Conventional laptops are getting lighter and last a lot longer on a charge. The extra bulk of something like a current Macbook Air vs an iPad isn't much but it's a vastly more capable machine.

And, even if we do see an increase in more hybrid devices like the Surface, you can't just blow up a touch screen app to 24". Specialized tasks will still require specialized software.