There is an expected announcement about upcoming upgrade of Bitcoin core version 30, it's going to allow people to send an arbitrary data into Bitcoin op_return script and with this, miners are going to be making money from the bytes included in this transactions, I think with such technology it is going to be a way for miners to make incentives instead of depending on block rewards that deplete with time, there is going to come a time when block reward will be less than cost of production even with pool mining.
It's also possible that fees will be another ways for them to keep the network going but a mix of this on the Bitcoin network is going to bring revenue and fees for miners to make money rather than depending on something that is going to get slash with time. If Bitcoin price becomes stagnant for a wile, it's going to be a challenge because nobody can tell where Bitcoin price will be in the future and the transaction fees are not that big despite the fact that onchain activity is not bad.
It can be good initiatives to expand utility of Bitcoin blockchain and bring more income to Bitcoin miners which are vital parts of Bitcoin blockchain and work. As a Proof of Work blockchain, without Bitcoin miners and their mining operations, Bitcoin blockchain will be less lively or even dead so if this initiative and other initiatives in the future work well for Bitcoin miners, there will be not such a question "What will happen after 2140 year when all 21 millions of bitcoins are all mined?"
So far, without this initiative, Bitcoin miners still have good income already but I think the intiative makes sense as Bitcoin developers must never stop their programming jobs for strengthen Bitcoin blockchain.
