From the point of view of people from the past, we currently have unimaginable computing power, when you can crack old crypto systems on your home computer in seconds, but it really doesn't mean much, because crypto systems evolve to match new challenges. Quantum computers are still extremely theoretical/experimental, but we already have algorithms that can resist them. And algorithms will keep improving in the future, so I'm sure the will have an upper hand over quantum computers.
Exactly. Algorithms and technology will continue to improve over time. We may have seen the advent of Quantum Computing, but existent technologies could adapt to this trend in no time. Bitcoin could easily implement a quick fix to become resistant against Quantum Computing attacks. I'm sure many miners will agree to this change, as their money is at stake. In the case of Google, I believe that the company has been full of hype than anything else. Their claims of "Quantum Supremacy" must be questioned, in order to determine with precision the impact it'll have over traditional (classic) computers of today. Slowly but surely, Quantum Computing will improve to a point where they'll be able to replace existing computers. Google might as well use its own Quantum Computer for good instead of evil. The field of Quantum Computing can be extremely beneficial for the improvement of Blockchain technology's performance within the mainstream world.
Considering that Quantum Computers are still in their infancy, they don't pose a threat to existing cryptocurrencies yet. Developer teams of prospective cryptocurrencies (like Bitcoin and Ethereum) should take a step further by implementing Quantum-resistance before Quantum Computers become a real threat to the Blockchain industry. We still have plenty of time, so I wouldn't worry much about Google's Quantum Computer destroying Bitcoin today. Just my opinion
