I think if we are at the point in technology that a QC can be made that can break SHA256 in a relatively trivial manner
Wrong; quantum computers need to run for 2^80 steps to find a private key mapping to a given 160 bit public key. That will remain infeasible for decades to come.
however the threat of QC is 51% attack, not directly breaking the key-pairs but while cryptographers think in probability space (2^80) of breaking something secure (in theory), there are Cryptanalysis methods out there to find shortcuts (in practice) and decrease the steps they need to pass:
https://en.wikipedia.org/wiki/Cryptanalysis
the most important point of failure that I see in asymmetric encryption is running a Random Function in key generation stage. providing real randomness is one of the hardest problems that I ever seen - because what you think is random at first sight, in fact carries a hidden pattern inside. so most of the time random number generation is where Cryptanalysis begin their job from.
