From 2099 till 2140 (when the last satoshis will be mined) there will only be one bitcoin mined. By the end of the century, supply is virtually fixed and limited to the maximum of 21 million. For the following forty years, miners will be mining only one bitcoin...
With most transactions (and most tx fees) being forced onto second layers, it will be interesting to see how this impacts miner incentive and their desire to secure the blockchain.
My best guess is that by that time, Bitcoin will have become a minority player in the space due to its inability to evolve.
In a scenario where 2nd layer solutions are widely used with a large number of micropayments, the on-chain
settlement transactions would still be needed. Further, in such a mature scenario, one-time, large value transactions involving business entities would still be on-chain and should provide remuneration for the miners. If anybody thinks that there won't be a fee-based future for miners, then you should not be in crypto. Deflation and fixed supply is what makes it work.
And its 2099 we are talking about. By that time, a number of additional features would already have been added. For bitcoin to become a minority player, another project with the same level of network effect and decentralization would need to evolve. That doesn't seem possible with the kind of money-grabbing, vaporware peddling people behind other cryptocurrencies.