Quantum computing will be available before the last Bitcoin is mined so:
How does Bitcoin defend itself in a post-quantum world?
How will this affect the mining companies who have made significant investment into ASICs?
How will this affect dormant wallets (e.g Satoshis wallet) from being cracked and liquidated?
P.S. do not avoid the question by saying "quantum computing is so far off into the future..." Or some other low-energy, beta response