quantum computers are great at solving(dumbed down for simplicity) 4D puzzles but not so much efficiency gain on standard binary 2D puzzles
so while some 4D puzzles are near impossible for 2D computers, quantum can handle them better.. however the opposite way round trying to get a quantum pc to do a 4D solution that also applies to a 2D method loses its efficiency because the solution needs to be understood by normal binary computing

also ASICS even just one is the equivalent of 200million normal pc's, so if there are 2million asics, thats the equivalent of 400trillion binary pc's making the blockhash, which a QC computer still wont compete against

If I remember correctly, since the early days of entering the market, I have heard rumors about quantum computers but so far, I have not seen any threat from it to bitcoin or the crypto industry. It's all just conspiracy theories, hypotheses, rumors, nothing to worry about.

In the future, if quantum computers can develop and reach that level, perhaps bitcoin developers will also find a solution to upgrade bitcoin to adapt to everything. Quantum computing technology is evolving but bitcoin and the crypto industry are not standing still, everything is still being developed so I don't think they will pose a threat to the crypto industry.
But in all fairness, the future is unpredictable so depending on the situation, we should have a specific response plan.

If it could crack the Bitcoin network and break its algorithms, that would be a huge threat. But if there’s no problem there, I think Bitcoin will stay just as secure as it is now. The big thing to look at is mining. Traditional mining might get outpaced once quantum computers become available because many miners would likely switch to quantum mining as it solves cryptographic puzzles much faster. This would push smaller miners out of the game, making the mining process more centralized, controlled by those with enough money to use quantum computers.

Bitcoin and super-computers are a complex and dynamic topic, but the way it's unfolding seems likely to affect the future of cryptocurrency and the security of blockchain technology.

Super-Computers and Quantum-Computers Will Threaten Bitcoin Security. It's been heard for a long time now but I'm not surprised because we can see and know how much technology is progressing and when quantum-computers are released we will see who Bitcoin is. Different types of technologies will come to protect against threats. Because the quantum-computer will not happen overnight, it will take a lot of time to be released and when it is released, there will be something out there to protect BTC, so there is nothing to fear about it.

Quantum computers can pose a serious threat to Bitcoin, in particular, to its cryptographic security, for instance, breaking with Shor's algorithm that may expose private keys from public Bitcoin addresses. But the crypto world is already developing quantum resistant encryption techniques with which to protect Bitcoin and other blockchains. While the current security of Bitcoin, such as the SHA256 hash function is somewhat resistant to quantum attacks, further upgrades may well be required to keep up with the development in quantum technologies.

Other concerns include how supercomputers could centralize mining in those entities that have access to such technology and may, therefore, undermine Bitcoin's decentralized architecture. With such prospects in the air, there are reports of developers considering countermeasures, from hard forks to quantum resistant algorithms to even a consensus algorithm change to PoS, said to be more resistant to quantum attacks than PoW is. It means that the crypto ecosystem would, by 2040, have adapted to the fact that there is most definitely going to be an improved structure of security or new framework coexisting with quantum advancements rather than a total collapse.

Don't place hope on another technology battling another.
And besides would the government allow the releases of Quantum computers to the public well knowing that it could pose a threat to their security more.
Well they can use it themselves for an attack on the blockchain
Success is probable but lean more towards failure but it could be used to crack wallets especially for individuals who use same address.

I would say that some put BTC as an invention and the tool for decentralization of some processes first and foremost, not as a tool of investment, however, as time moves on, more and more people consider it only for such reason - to get money out of it eventually. It's not seen to be learned and innovated upon.
I do understand where this belief comes from, however, I do not see it happening 

We can only hope that the blockchain will be able to adapt and thrive even with such machines in place.
I think the crypto space will be able to do so  Together.

Im also advocate that if QC can decrypt the SHA 256, it can also fortify not even AI tech can break it at that point. Things are moving so fast in this era that this technology has to improve a lot to avoid becoming obsolete at any time. Even gas fees are going to obsolete at that time so many crypto's that are depending on it might have to think otherwise.