Bitcoin has a limit to the number of tokens it will release. That number is hard-coded at 21 million. The estimated date of Bitcoin issuing its last coin is believed to be in the year 2140. No one can predict what will happen at that point, but miners will always earn some profit from transaction fees. Plus, users of the blockchain and the Bitcoins themselves will be incentivized to protect the network, because if mining stops, Bitcoins become vulnerable and so does the data that has been locked into the blockchain.