Interesting to think how many 10^6 faster gates would be needed to do the work of 10^9 at the same speed. Say take the 8086 and make it a million times faster. At about 30K transistors and 5MHz. A photonic 8086 apparently would run blindingly fast around anything available now.

Serial speed is always a gain up, no questions asked I guess.

Obviously all of that is over simplified, and not considering other components to any system that would be built (but hey, it's not like any of this is happening tomorrow anyway).