The network security model then relies entirely on fee incentives. If transaction volume remains high enough, miners stay profitable. If not, hash power could decrease, which might affect security assumptions.
As for hardware: most modern BTC mining uses ASICs, which are highly specialized and not practical for AI workloads. They’re optimized for SHA-256 hashing and can’t be easily repurposed. GPUs, on the other hand, can be redirected to AI or other compute-heavy tasks.
The bigger open question is whether the long-term fee market will be sufficient to sustain miner incentives without block subsidies.
^^^ This. Fees are already included in block rewards and (compared to the block rewards) are pretty paltry. Unless the value of Bitcoin goes way up, I don't see a resilient network sticking around with enough hashing power to keep out a malicious actor / bad state actor.
Edit: These charts should give you an idea of how much fees represent in current blocks.