You greatly under estimate the power of the profit motive and a market. Bitcoins will continue to be generated as people find more clever ways to reduce hardware and power costs. A lot of people are generating them at zero cost by using their employer’s computer. It’s unfair to the employer, but it is the reason why bitcoins will continue to generate. The current algorithm for difficulty is fine the way it is.
But let’s assume you are correct and people stop generating bitcoins early. So what? There will always be a market price for the remaining bitcoins.