What is the actual risk to long-term BTC?

It's easy to understand the arguments about how the price can't do anything other than keep going up -- finite supply + increased demand = ever-increasing value

We're close to 95% of all possible BTC mined... and than number will be 99% in 10 years. At that point, effectively, the new added supply will be minimal, but the demand will be at a rate much higher than today. Soaring prices are inevitable. What would happen to the gold price if there were suddenly no more gold on earth to mine? You'd have to get your gold from the existing supply, and prices would be 100x what they are today.

OK, we all understand that.

So what exactly could possibly prevent the scenario of BTC continuing to rise? The only one I can think of is that the whole thing "breaks" -- like someone manages to hack their way to 50.01% of the reserves and then wrecks it. Or the encryption is broken. Or quantum computers manage to crack their way into it and ruin the inherent trust offered by the blockchain.

There's really no version of "all the gold in the world suddenly melts into oblivion", and that's part of the persistence and non-correlated inherent value it holds. Fiat currencies aren't backed by gold anyway... like, what's backing a USD? Everyone's belief that it's worth something and convertible to something else of value.

I can keep rambling here, but the real question is simple -- what could happen to undermine BTC value in the long-term?