I believe that the landscape of hardware is entering a change on par with the "killer micro" transition.  Its main victim will be the desktop computer.  While it may retain the letters "PC", the title of personal computer will be taken by a device that fit into your pocket.  Whether that will be the smartphone or not, I will explore that later.
There are other roles desktop computers fill, for example in offices.  In these uses, I think that timesharing will come back.  Individual desktops have to be capable enough to cope with the maximum load they may encounter, and their hard drives are next to useless.  Since so many things are already stored on a server (as a network drive), and a server could even out the load much better and thus require much less redundancy, this arrangement appears to be a win all around.
This also points out the niche for the desktop to still rule: high-end workstations for graphics designers, engineers doing CAD work, and the gaming rig (which may or may not fuse with the gaming console).  This is much the same area where the desktop computer first arrived, if you are keeping track.
The really personal computer is something you can carry around at all times.  Currently, this is the smartphone, but in my opinion this is a temporary situation, due to the inherent faults of the device.  Which is basically the small touchscreen being a terrible input device.