What about the halving after that? Or the second after that? In less than 20 years from now, the block subsidy will be less than 0.1 bitcoin. Block space has to be valuable.
In 20 years, Bitcoin could be worth far about $1M. That puts 0.1 Bitcoin per block at 15 million dollars per day. If blocks are ten times larger (and still full), just 1 sat/vbyte is enough to double that. I'm much more worried about the current damage done to the Bitcoin ecosystem: if people can't make transactions, they can't use Bitcoin. If Bitcoin can't be used, it can't grow. I'm not worried about block rewards 20 years in the future.