Right now we're approaching about 17 million out of 21 million possible bitcoins. When we reach the max supply, what incentive would miners have to continue mining and verifying transactions? Sure they can still collect fees, but why not mine newer and more profitable coins where they have the chance to collect both fees and new coins?
What's stopping the entire blockchain from grinding to a halt, prohibiting users from conducting transactions, and thereby making bitcoin worthless?
You are wrong. it is the opposite. if bitcoin cannot be mined anymore, the bitcoin value will much more increase.
because the demands still keep increasing with the supply of coin which is not increasing, this will result a high price in bitcoin.