I think even if the last drop of bitcoin is mined it will still continue in the market.
But the problem for the investors/buyer is that it will be a high because theres no more bitcoin to be mined.
But the good news for the seller because they would gain a lot from it.
I think bitcoin will last for a very long time because we cannot stop it from circulation and all the holder will continue to sell because if they cannot exchange it, be it product, services, currency then whats the use of it.