IonQ says they would have a machine powerful enough by 2028.

That bar only holds if the size needed to beat secp256k1 doesn't go down as it has many times over.

How much is exposed

• about 6.3 million BTC in outputs whose public key is already visible Source

• about 2.3 million BTC dormant and unlikely to ever move to safe addresses Source

• 50 to 65% of all ETH has an exposed key at rest, by one estimate Source

Assuming, Bitcoin does migrate on time. I don't see many options here.

Just locking out those millions? That would cut the supply significantly. So a rise of the price?

Centralized exchanges probably will automatically migrate but a lot of holders hold their own keys and they'd have to all migrate on time? What is the plan? When does it get to dangerous to hold? So a price drop then? I am pretty confused.

Quantum threat tracker -> Bitcoin