> so far demonstrated to 770GHz for one CPU

That's not a CPU, it's a simple circuit. From the article, "Simple superconducting logic circuits have been shown to operate at speeds of up to 770 gigahertz."

Exotic semiconductor transistors can switch that fast, record being over 800GHz I think. Regular transistors of the type in your phone can probably do around 200-300GHz. Not to say there could not be revolutionary designs opened up with superconducting wires or switches, just the switching speed itself doesn't necessarily tell us one way or the other.