> by 2050 when, my bet, there still won't be any remotely viable QCs

I hate to be that guy, but I'm 52 now and I've been hearing about how Quantum Computing is going to revolutionise everything in the next two years, since I was in primary school and ZX81s were state-of-the-art.

At least a couple of manufacturers offered a practical and afforable(-ish) transputer-based system in the 80s that you could have actually gone out and bought.