Well this is because the word "computer" needs to be dismantled a bit.
Computers as a personal mainstream entertainment device will eventually work much like television. Data retention policies will be at the whim of the content distributor and consumers will select from sets of content dictated by different price packages.
Computers as midrange workstations for engineers, artists, musicians, and scientists aren't going anywhere and will be the same as they always have. Same goes for the NOC and the Datacenter. Devices that collect and analyze data will work much in the same way. The people that will create and maintain the consumption paradise will continue to do things on traditional configurations. The biggest change here is that display and input systems will continue to diversify in form and function. However, the machine will still be a rectangular block, with all the internal components you are used to.
The million dollar question is how will people that do mostly office-productivity work? For instance, the person at the dentists office that makes the phone calls and does appointment and billing management. Most could probably get by with a desktop version of a smartphone, but nobody has produced the right one yet.
But this doesn't mean that say, the traditional computer will exodus from the dentist office. Just the opposite. They are in every room now, hooked up to cameras and xray machines, talking to redundant servers either on or offsite.