The total amount of 21 million doesn't need to be changed because the price will likely be very high, and we already have 100 million sats to divide each bitcoin.
so if 2059 comes along and 300,000k coins from 2009 blocks never moved and you reset them back.
Recycling burned, old or lost BTC coins would involve modifying the blockchain, which I don't think is an adequate solution because it undermines the idea of "Bitcoin's immutable blockchain".
letting myself be carried away a bit by fiction a more viable solution in the future, if ever needed, would be to create a smaller unit of denomination, a kind of micro-satoshi, which could better handle transaction amounts.
but this would be in a very, very distant future.