Today's computing mantra is "One keyboard, one mouse, one display, one computer, one user, one role, one administration"; in short, one of everything. However, if several people try to use the same computer today, or cross adminstrative boundaries, or change roles from work to home life, chaos generally ensues.
Several hardware technologies will soon push this limited model of computing beyond the breaking point. Projectors and physically large flat panel displays have become affordable and are about to take a leap in resolution. Cell-phone-size devices can now store many gigabytes of information, take high resolution photographs, have significant computation capability, and are small enough to always be with you.
Ask yourself "Why can't we sit with friends, family, or coworkers in front of a large display with audio system, and all use it at once?"
You should be able change roles or move locations, and reassociate with the local computing environment. The new mantra must become "many" and "mobile" everywhere "one" has sufficed in the past.
Change will be required in many areas from base system, through the window system and toolkits, and in applications to fully capitalize on this vision.