Maybe what you mean is that as the price increases in the future, the exponential growth will slow down, which is true. However, what makes the argument is that bitcoin is going to be scarce as well, that's why it is the most sought asset in crypto because of this one. Yes, the growth might stall, but with more people looking to buy at whatever price it is, I doubt that there are less buyers that are going to enter, on the contrary it might balloon as everyone is looking to make bigger profits in the future.
I am also thinking about this issue. The higher the Bitcoin price, the fewer participants will be. Because investing in Bitcoin has many unpredictable risks. Once there is a risk, you will lose nothing. So no one wants to lose money. That is why they rarely buy. This in turn led to another result. When few people join, the rewards from Bitcoin and campaigns will be very high. That's what I'm expecting.