I believe we would have a hard fork if a flaw was discovered and didn't course complete damage to the Bitcoin network. The world of technology keeps changing over the years.
This has already happened, and the details of what happened are back to block 74638 aka CVE-2013-322, where it required a hardfork and the network was divided into two parts (one of them dead). down time was about for 6 hours and 20 minutes.
CVE link:
https://www.cvedetails.com/cve/CVE-2013-3220/Bitcointalk link:
https://bitcointalk.org/index.php?topic=822.0It is true that the price will be severely affected, and we may witness a correction of more than 50%, but if something defective happens to SHA-256, believe me, all stocks and economies in the world will decline frighteningly.
Some time ago I read somewhere that there are already quite some efforts to fight Quantum Computing in terms of encryption algos (collision finding or something like that), but not sure they can easily be applied to Bitcoin in matter of days. Even days can be too much time! I think this is a valid concern!
Quantum Computing and RSA is a FUD and only risk with some P2PK.
Don't re-use your address after sending from it (always use new unused address when HODLING) and will be safe.