centralized organizations---military, corporations, banks---can harden their systems extremely quickly if necessary. bitcoin cannot. millions of coins will remain vulnerable.
Judging by how most organizations outright refuse to upgrade their systems in a cost saving measure, it's debatable how quick that'll be. I'm not sure if there'll be a standards defined by then and whether consumers can roll out the update in quickly.
how about in 10 years? how about when bitcoin is bigger than gold's market?
i just don't understand the blind optimism. everything boils down to "even if it happens, nobody cares enough about bitcoin to attack it" or "everyone on the network---including the former owners of lost coins?---will magically move their coins the second before QC is a real threat". neither of those are believable to me.
What if in 10 years, Bitcoin drops to $10 per coin? There's both ways this can go of course.
My take on this is that governments are not primarily very interested in monetary incentives, if you consider that most of the country's GDP is way more than Bitcoin's market cap and you have to include the cost for running one as well and AFAIK, current technology is nowhere near the efficiency that we need and the difficulties of running one for long periods of time, I think it's close to 0K?
I don't think that there is any viable solution to stop potential attackers to benefit from the older coins and most of the current proposals are merely based on the economics of doing it. If you can propose a way to stop attackers from siphoning those funds without forcibly taking it away, I'll totally be behind that of course. Otherwise, the funds will eventually be stolen, when quantum technology gets cheap enough. I don't believe that either of the statement will be true but I do however believe Bitcoin will not be the first to be exploited.