From what I understand, if you chill everything down then you also change resistance in the semiconductor along with all the other properties, so it probably isn't as easy as just replacing the copper wires.
From the sources I've read, there aren't any major issues running CMOS at 77 K, you only run into problems at lower temperatures, less than 40 K. I guess people aren't seriously trying this because it's probably not much harder to go directly to full superconducting computers (i.e., with logic gates made out of superconductors as well) which offers a lot more benefits. Here is an article about a major IARPA project pursuing that. It doesn't seem safe to assume that we'll get AGI before we get superconducting computers. Do you disagree, if so can you explain why?
There was similar interest in superconducting chips about a decade ago which was pretty much the same story - DARPA/IARPA spearheading research, major customer would be US intelligence.
The 500 gigaflops per watt figure is about 100 times more computation/watt than on a current GPU - which is useful because it shows that about 99% of GPU energy cost is interconnect/wiring.
In terms of viability and impact, it is still uncertain how much funding superconducting circuits will require to become competitive. And even if it is competitive in some markets for sa...
At some point soon, I'm going to attempt to steelman the position of those who reject the AI risk thesis, to see if it can be made solid. Here, I'm just asking if people can link to the most convincing arguments they've found against AI risk.
EDIT: Thanks for all the contribution! Keep them coming...