The problem with BTC and other currencies will be that you will no take any $$ - > banks are already starting to refuse transactions.
after 2025 BTC , ETH and so on will be worth real 0.
How so? First of all, think outside the box: you can earn and spend Bitcoin directly, without touching a bank. That was actually its main idea.
Furthermore: you can definitely buy and sell Bitcoin peer-to-peer - again: how it was intended.
Peer-to-peer electronic cash.
I believe he is talking about the fact banks and traditional financial institutions still play a role when comes to provide liquidity to the Bitcoin market, mostly in the form of people trying to buy Bitcoin and other alternative cryptocurrencies with FIAT on exchanges which allow to do so, like Binance or Coinbase.
It does not sound impossible banks would block such purchases in the future, in my opinion (debit and credit card). On Binance P2P it is already advised not to tag or add any crypto-related description to the transactions to avoid flagging by banks.