I think disruption could only occur through a revolutionary form factor or revolutionary functionality. The most likely avenue to chase in this area is the Internet Of Things; controlling and talking to things around you. But even that is getting fairly saturated.

In my fictional world, people didn't try to rewrite X Server with Wayland and Mir and SurfaceFlinger, they optimised X and compiz and made it modular, so it maintained all of it's cross-platform, cross-network robustness, but also became incredibly fast and beautiful, able to scale from smartwatch displays to vast walls of connected display grids.

And nobody made a Linux kernel fork (Android, grrrr) that fragmented the hardware market for 8 years (so far).