Yes, I seem to be on a kick about this. sorry.
There are two limiters to shrinking the computer. The two limiters are input and display. Between voice, touch, and several nifty ‘virtual keyboard’ systems out there I think input can be safely ignored. (There’s a device that will project a keyboard onto any flat surface using a laser trace. It then uses a ladar-type process to determine where you’re typing on that board. It’s about the size of a prescription pill bottle. Just for an example, you see.)
The display, however, is a killer. It’s the reason so many sf stories go to mapping in the brain. Take a look at a game display again. Seriously, LOOK at it. Now picture using it for reading a business report or textbook. Heck, picture half a dozen of your favorite websites on them.
FWIW, I’m going to make another small guess here. Until/unless someone figures out how to make an expanding screen or eyeball mapping or neurolinks, the only dimension that’ll shrink is thickness. That means we’re going to see two screen sizes for portables. The first is ‘about the size of a cellphone’. The second is about the size of a paperback book.
What this also means is that contrary to yesterday’s impressions, desktops won’t go away. Larger screens are just flat easier – easier on the eyes, easier on the mind, etc. Everything else might change, at least a little bit. However, it’s still easier to work at a desk, and that means you can have a bigger container which in turn allows more stuff. Graphics tablets and keyboards and extra memory and maybe more (and dedicated) task processors and, well, you get the idea.
We’re past the point where the box needs to be huge. We’ve got various input devices that make our actual needs suprisingly tiny. But our eyes are still the original system and that means what we look at has to be big enough. That’s the anchor. That’s what will control most of computer design of the next several years. Whatever else you do, you have to see.