Hedera has a fixed supply of 50 billion coins.
Multiple mechanisms are in place to prevent more HBAR from ever being minted:
1) The number of HBAR minted (50B) has been coded into the network software.
2) In order to change the code to mint more HBAR, members of the Hedera Governing Council must unanimously vote.
3) Council members may face reputational harm if a decision is unanimously made to mint more HBAR.