You are asking people that have been asking same question without getting the right answer themselves, the only way for everyone to know what will happen to bitcoin is when the remaining bitcoin has been fully mined. Anything you are seeing now are just mare speculation and nothing specific. Although many people believe that miners will be making their money from transaction charges, but we will only know about this after the entire bitcoin has been mined. But personally I believe that there will be a way for miners to get compensated when the entire bitcoin has been mined. So let's not get ourselves worked up over what will happen to bitcoin, because I know for sure that bitcoin will be here forever.
No one alive now will live to tell the story of what will happen to bitcoin if all bitcoin have been mined in the year 2140 because we would all be gone. If all the bitcoin are mined, miners will benefit only from transaction fees because by then bitcoin will be very expensive and mining fee too will be expensive than what it's currently.
Bitcoin will become very expensive because no new bitcoin will be mined and many will have sold out their bitcoin to the government and big companies who will be holding major of the coins with them in their bitcoin reserve. Just my thinking.