I buy those overpriced Macs. You get what you pay for. If you develop apps or design things, there are performance benefits to a Macbook, iMac or Mac Pro. With that said, you're talking 10-15% of users with those requirements at best. If you're browsing the internets, Facebook, blogging, and Skyping, then a Macbook is complete overkill.
Honestly, if it wasn't for my design and development, I'd content myself with a good Chromebook or Netbook. I'm intrigued that Photoshop might be coming to Chromebook.
Quantum computing will be a game changer once it's advanced and further downsized. We've been purchasing small form factors for work (they were running 8 year old machines for what little overhead they need) and it's like blowing the minds of a lot of the nontechnical employees. (I'm thinking that tablets are close to being par with what we use.)
The only limiting factor I see is the human interface. I've noticed a lot of people use tablets for browsing, but don't do more complicated tasks and supplement them with a keyboard to do blogging, emailing, etc. I still think we need the next iteration of interfacing to see what will happen to PCs. I've known a lot of people to cool on how they feel towards using a tablet, because it's still too clunky for some things.