One of the biggest revolutions in computers that I can imagine would be: genuine three-dimensional displays. Replace that flat LCD screen with a projected, realistic reality, and everything we know about computers communicating with users would change.
Of course we're not just talking about change for the better. Imagine an error message box that seems to fly right at you, stopping just in front of your face, to get your attention. Or the first lawsuit by someone with a fear of heights, who almost fell into their computer when an enormous pit opened in front of them onscreen.