Well you posted this in the "Economics" section, so let's make this about economics.
People have an amount of BTC. The higher the value of their BTC, the more likely they are to keep it in safe locations or spread it between different places. So the chance of them losing their BTC decreases exponentially as the price rises.
If they lose BTC, the supply decreases, therefore making the remaining BTC supply (marginally) more valuable and making people less likely to lose it. So it never reaches a point at which there's not enough left.
So basically, no. It's impossible.
As long as storage and transactions are handled by humans, there is no way to avoid human errors, regardless of the assets value. Sure it is less likely to be lost, the higher the value. But will it ever be totally secured just because it is of a certain high value.
I am not convinced.
Then it will just get reduced and reduced in the max supply which leads to a much mlre limited supply.
I doubt that all 21 million bitcoins will be lost, or even half of it or a million of it. People tend to keep their assets secure especially when its valuable so they may lose a little bit of bitcoin now and then but not that great actually.