Hi @davidekpin this is a technology I have been following with interest so I was very happy to see your post about it!
IMO from what I have researched so far I think Quantum computers and classic computers will coexist because they are geared towards solving different types of problems. What we will start to see - I think - is cloud based Quantum computing capability that people can tap into. It's already started with IBM allowing people to use a quantum computer online .
From what I understand Quantum computing will start to get very interesting for us at 1000-10000 Qu-bits were we will be able to solve real-world problems that were NOT able to be tackled by Classic computers. One such problem is being able to model complex molecular bonds. Regarding, decryption of SHA-256 (defacto standard encryption atm) we will need much bigger quantum computers. I remember reading that the problem of tackling decryption with Quantum computers is not as trivial as first thought.
I appreciate your comment, and agree with most of what you have said especially about co-existence with classical computers. But there is a big problem, do you think that the near space cooling requirements of quantum computers is achievable? As qubits are very unstable