When the whole bitcoin have been mined there's nothing to worry about, the orice and value of bitcoin remains and here miners get their rewards from the incentives of the transaction fees levied on every transaction made, the volatility is neither a threat to waether bitcoin in failing but by then, it will still be maintained as that's what drive the push for buying and selling of bitcoin in the market, the price is likely to go high drastically because the more the adoption the higher it's demand and price will indeed increases as well.
In theory it is like that, I hope that theory will not be broken. In addition, I hope that confidence in the value of bitcoin will not be lost either. That's why bitcoin becomes valuable. If trust is lost then bitcoin will no longer be valuable.
Indeed, if the demand is increasing and the amount of the remaining goods is reduced, it will cause an increase in prices. It is included in the legal theory of supply deman. Although indeed I still have a little problem with scalability and transaction costs. This results in slower transactions.