As all the bitcoins are mined, finishing in the year 2140, the incentive to maintain the network has always been intended to be the transaction fees--and they already are.
Tagging
@Gamemaster1379 for the response on the subject.
I haven't looked into the specifics of Bitcoin's long term strategy, but that is correct. In networks such as Ethereum, mining fees are already what funds the project's miners. I'm not aware of Ethereum's blockchain itself paying out for it being mined -- the payouts are from others wanting their transactions to be included in that block -- thus the miner includes them for the transaction fee that Ethereum users are offering.
While bitcoin doesn't emphasize this as much, it's still a part of it as well and will likely become more front and center once all Bitcoin is mined or the payout is so astronomically low.
I think a lot of people don't actually realize what most cryptocurrency (including Bitcoin) mining really even is. You often hear it's "solving complex equations", but what for -- not a lot of people know. Most crypto mining is for adding the next block to the blockchain. A block is a compilation of database records -- or more specifically, ledger records of who is spending what on the blockchain. So even after the blockchain itself stops rewarding people for mining -- people will still pay to have their transactions included. Thus, so long as someone wants to move Bitcoin (or whatever crypto) from wallet A to B, there will always be someone who will be mining. Even if the blockchain itself is no longer paying out.