Normally,after all bitcoin have been mined no reward again,there will be an end of inflation on Bitcoin and the increase in asset scarcity,miners will then only

 be remunerated through the transaction fees of the Bitcoin network.

Along with reliance on transaction fees, miners would need to evolve their equipment due to increasing competition, by then there will be more powerful

technologies so only those who can afford  stays in the game or they could explore alternative cryptocurrency options to seek profitable mining

opportunities.