Once all bitcoins have been mined, there will be attempt at finding 'lost private keys' ; possibly using Quantum computing, or is this utter nonsense ?
We don't know when but I believe that this scenario is probable once a QC becomes practically usable for breaking ECC. Then, there will be two types of "miners" 😅. The thing is, there will always be maximum of ~20,999 BTC and not more and the live wallets will be already QC-resistant.