Somewhat ironic question, but as ETFs holdings of BTC continue to grow, is there a possibility that the custodians of those ETFs start to have a backup plan for ETF holders or create an alliance to push a fork forward? The management fee those companies generate is non-trivial, so they're incentivized to stay ahead of this.

Now, of course, the irony here would be traditional finance infrastructure winning out over decentralized, which could definitely deal a psychological blow to BTC's perceived value... but it's something I've been thinking about lately as this existential threat rises on the horizon.

In the absolute disaster scenario where the ecosystem is taken by surprise by an adversary with a CRQC, regulated custodians could form a consortium to reconstitute a new quantum-resistant version of bitcoin, pooling their ownership ledgers from before the disaster to reinitialize the blockchain and consigning to oblivion all coins not held in custody.

Yes, if you read the fine print on the ETFs they tell you what they will do in case of a fork. Usually their custodian picks the "winning" chain at their discretion. There's a similar (although reversed) situation with stablecoins.

Microstrategy is already pushing/funding quantum resilience for Bitcoin, so yes!