My dream computer is probably a phone.
It’s a box, about phone sized, with a full-size touch screen, Wifi and Mobile data capability, running unix based OS with touch-screen optimised UI, and having enough data storage to put the majority of my stuff on it locally. The rest is encrypted on a server somewhere (some people will run their own, others will buy commercial versions, companies would have shared ones). That’s probably Ubuntu One, or something similar.
A current-gen version of this has HDMI and USB out, but could probably be replaced with Thunderbolt. The Thunderbolt could be used for a larger screen version of the touchscreen-optimised OS, at which point you’ve got a tablet, or you could plug in a keyboard and/or mouse as well, at which point you’ve got a full PC analog. Possibly there also exist docking stations with more CPUs & ram in, or maybe the CPU in the “phone” unit scales based on available power capabilities. The important bit is that the data, the control and the “machine” itself is a small pocket thingy. Ideally you don’t have to plug anything in anywhere, and this is all magically done over wireless. Plus, it’s entirely secure and never breaks.
See? I’m a pundit now!