How vulnerable are dormant crypto holdings in the post quantum era?

Many blockchains assume a future upgrade to post quantum security will simply protect everyone. That assumption breaks down for coins in wallets that can no longer sign anything. Lost keys. Abandoned wallets. People who have died. Early miner rewards. Any address type that has already revealed its public key.

These holdings cannot upgrade and they cannot defend themselves.

Bitcoin is a prime example. Some of the earliest coins use P2PK address formats where the public key is already visible on chain. If a quantum computer becomes capable of breaking ECDSA, those coins are immediate targets. Taproot becomes exposed as soon as it receives funds. Legacy and SegWit have time based protection only because their public key is revealed when spending.

Here is a summary of current situation:

https://preview.redd.it/mltb1297xs2g1.jpg?809&format=pjpg&auto=webp&s=a09e7739119c2515c826d1ccd76bbf7db30b5bff

If practical quantum computers appear before a coordinated migration, dormant and unmaintained coins are the first in line to be drained. They are easy to identify and impossible to secure.

Key questions for long term holders and protocol developers:

• What happens when keys cannot be rotated?
• Should there be a preemptive plan for permanently inaccessible coins?
• How does the network react if thousands of old UTXOs begin to move under attacker control?
• Is post quantum secure technology already available and would integrating it materially change the blockchain today?

This is not a fringe scenario. It is a structural risk and it deserves serious attention.