The world doesn't operate with code as law. If somebody steals all the bitcoins in the world then they'll just fork it [1].
A significant amount of bitcoins are held by known entities (exchanges) so it's pretty trivial for institutions to keep their coins after a fork. Those of you self-hosting might have some losses.
+1, the tokens from before a quantum hack will be transferred to a new fork. So at that moment, the value of BTC will go to 0 and the value of BTC v2 will take the value of BTC.
However at the moment, the community seems to be leaning towards pay-for-quantum-resistance [0]
I'm not so sure this will apply to BTC. It more or less has the staying power that it has because it hasn't changed at all, in fact pretty much everyone involved with it has resisted changing it, and it's not obvious there's anyone with enough political capital to make the fork, because anyone, right now, can make a fork of BTC and none of them have ever done well.
A significant amount of bitcoins are held by known entities (exchanges) so it's pretty trivial for institutions to keep their coins after a fork. Those of you self-hosting might have some losses.
[1]: https://en.wikipedia.org/wiki/Ethereum_Classic