All using extremely efficient tiny lithography processes that make powerful and complex CPU / GPU's (22nm at least), that use a more 3D core-matrix. To cut a long post short, probably little in the way of PC's we know today, as we'll be able to fit it all into much smaller packages. "Smart-Devices" or "Tablet PC's", with the by-ratio equivalent output potential of the best enthusiast rigs on the market. Will this kill custom PC building. Maybe so, but I forsee less call, apart from in industry for faster, greater load carrying, and more complex rendering methods. We'll reach a point where the consumer can run all the latest games and software on their home devices (maybe a little more than 20 years away).
New non-volatile memory hardware will increase the capacity of these devices beyond necessary parameters.
The only thing I see getting in the way is enterprise and business. They will implement limitations, and force the consumer to buy new devices / hardware upgrades, regardless of the potential of the current state of hardware. Developers will likely be paid off or bought out and made to have their software run poorly on older hardware to encourage the adoption of new hardware. It's pretty bleak, but necessary to keep the economy rolling. It is an economy built on lies, but so is this one.
This reply is going somewhere that could result in a thesis on my views on the global governance structure. Technology!
But yes, if you were just to look up the recent advancements in theoretical, experimental and future consumer hardware, this is all well forseeable and not in any sense remotely fantasy. It could be really very very cool.
BTW (Addendum): While I'd lament the loss of customisation, and even will probably "rebel" against the adoption of "all-in-one" tablet devices, I don't see it as an overtly bad thing. It doesn't make sense to keep making big bulky machines, when it can all be done on a much smaller board. I do embrace, tentatively, a palm device that can output onto a 42" 8640p 20Ghz fold-out screen at 240FPS an utterly mind-renchingly beautiful vista, from Tamriel, wirelessly and seamlessly streamed. Passive Solid-3D too, naturally.