Everyone loves to talk about the 21 million cap, but we almost never talk about Bitcoin's dirty little secret: the year 2140.
That's when the block rewards officially run out. No more new Bitcoin. From that point on, the entire security of the network—the miners who protect it from attack—will rely only on transaction fees.
The theory is that a mature, global Bitcoin network will have enough fee volume to pay for its own security. But is that a guarantee? What happens if Layer 2 solutions thrive and most transactions happen off-chain, starving the main chain of fees?
Are we placing our faith in a future fee market that might not be strong enough to secure a multi-trillion dollar asset? Or is this a non-issue that the protocol will naturally solve?
Is Bitcoin's security budget a fatal flaw we're just kicking down the road?
I think that Bitcoin has survived over 15 years of doomsday and fud predictions. Betting against its ability to adapt has always provably been a bad move.
L2, miners and users are all aligned with the security of Bitcoin. They need Bitcoin to remain valuable. And they all want Bitcoin to become even more valuable than it currently is...So why would they want to drive it to ruin? Settlement is still required to be on mainchain and that requirement won't change.

I guess, in the worst case scenario, we could have big players (i.e. exchanges, BTC-related fund managers etc) to take responsibility for mining, or we could change the consensus algorithm to something else like PoS.
No, POS is cancer.
Literally cancer. POS would be the death of Bitcoin. With POW, hash rate follows cheap power, regardless of politics or laws. With POS, there would have been no great miner migration in 2017-2021 and Bitcoin would have become a chinese permissioned ledger. However, thanks to POW,
Minersminers simply migrated and proved that not even China can touch a POW Bitcoin.