I expected computers to use photonic circuitry by now. Maybe it is too complicated in practice to switch everything over to pulsed light instead of electrons. I haven't really kept up on the technology, but I imagine making IC's with photons is a bigger challenge for chemists than anticipated. Getting transistors to do the same thing for light that they do for electrons would certainly be challenging. Still, it would be awesome to no longer have to worry about cooling systems as much.