I'm guessing that increases in the processing power of CPUs & GPUs, along with a drop in power consumption, will mean that a desktop chassis will no longer be required. Of course external monitors will always be required for those that need screen real estate.
I think desktops will be around mostly for resource intensive applications and gaming. Nothing beats gaming on a new and powerful desktop.
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I agree. Many things you just can't do on a tablet, such as serious graphics. I'll always have a desktop for games and art work.