Nothing happens to them, they just stay in the wallet forever, or until they invent a quantum computer that can unlock the wallet.
The future of quantum computers are developing ,new versions of quantum pcs will be able to pass the restrictions of no-quantum resistant cryptocurrencies. Crypto holdings are only usable if person has a private key ,without private key it will be useless for that guy who passed away.
let's wait for the results, but I think there will be a key that can open the private key if the crypto is dead.
but there is also a possibility if the wallet is always updated and strengthened so that it will be difficult to open if you don't have the key.
so we won't know the results without us being there later.