> It would also be the absolute end of Bitcoin and derivatives, at least as far as I know.

Not really, because bitcoin only relies on the signature aspect of PKC. So, bitcoin could move over to Lamport signatures, which are not affected by quantum computing.

Lamport signatures are larger than ECDSA signatures, so blockchain bloat would be an issue. But presumably by then hard drives and all other computing specs would have increased substantially.

Here's an interesting article by Vitalik Buterin which explains how the transition could take place: http://bitcoinmagazine.com/6021/bitcoin-is-not-quantum-safe-...