What if transaction fees aren't enough to incentivize the miners to secure the bitcoin network? I think this is a potential problem we may see in the next few decades as the halving continues on.
It's likely miner with less efficient ASIC or more expensive operational cost (e.g. cooling and electricity fee) will shutdown their activity. And after next difficulty adjustment, other miner (who have more efficient ASIC and cheaper expensive operational cost) could continue mining not at loss.