The question is important for the future of Bitcoin.
Imagine a BTC price > $1,000,000 and more than 1,000,000 'shalecoins', coins with no owner
https://bitcointalk.org/index.php?topic=5134441.0 would become active.
The value of these coins would be > $1,000,000,000,000
How can that work?
There are two important.
Ad 1. If quantum computing managed to break private key cryptography in a way that it allowed somebody to control shalecoins, this would instantly induce a panic which would crash the price of bitcoin, so it wouldn't be $1,000,000,000,000 anymore, more like $1,000.
Ad 2. If quantum computing managed to break private key cryptography, we would have much bigger problems than future of bitcoin - all of the internet would be exposed to attacks it would be easy to hack anything from internet banking to medical equipment. Pure chaos would ensue and not many people would worry about their cryptocurrency.