Yes there will still be bitcoin miners when all 21m bitcoin are finished being mined. The idea is the main reward structure for bitcoin miners will move to transaction fees instead of bitcoin block rewards as we get closer to 21m bitcoin and the last block mined. If the price of btc rises enough and network activity on bitcoin increases miners could potentially make more in mining fees than they ever have before even after the last block reward has been mined. If you think Bitcoin will flip gold and a lot of financial and web transactions will move to Bitcoin it's definitely a possibility miners will be making huge amounts of btc just from transaction fees in blocks in the year 2140.