Opinion: It's practically certain that current Bitcoin public and private key cryptography (based on elliptic curve cryptography, ECC) cannot be made quantum-resistant without moving the funds to a new, quantum-resistant wallet. However, a method known as 'Vaulting' could be implemented if consensus permits. Changes to the protocol could apply a script to encapsulate dormant or lost key addresses behind a quantum resistant barrier protecting them from quantum attacks but still allowing the funds to still be moved by the owner using the original private keys. There are a few other ways that the dormant addresses can be protected but they are more controversial in consensus terms. Additionally, could it be that Tether is actually eyeing the lost Bitcoin? What do you think?