Yes, it is hard to speculate how much time or years it will take before the quantum computer that can break entropy, but it is easier for the decentralized Bitcoin ecosystem to adopt quantum resistant algorithm.
According to the information I once read by Quside, the platform that developed new generation quantum technologies for connectivity and efficient computation. There's already a team working on quantum cryptography (like code based cryptography, lattice based cryptography) and post-quantum cryptography, which are said to be classical algorithms to combat quantum decryption, so I don't see any reason why it will be hard to have the creation of quantum resistant algorithms in Bitcoin.
You are talking about the creation of quantum-resistant algorithms but I am talking about a different thing: adopting and implementing that algorithm in Bitcoin.
It's not as easy as saying we created this quantum-resistant algorithm and tomorrow we are merging it into Bitcoin. That's not how it works. You are going to see BIPs with proposals to introduce the new schemes. Developers will have to review it, test it, get community feedback. Bugs and vulnerabilities would have to be looked for and corrected. All this can take a long time. Remember Segwit, the blocksize wars, and the aftermath? Remember Taproot and how long that took?
A decision has to be made if the new algorithm will be introduced through a soft or hard fork. Either way, there will be new addresses and scripts and changes to signatures. Everyone will have to move their coins from previous quantum-vulnerable scripts to the new quantum-resistant one. The bigger the change, the more drama, fighting, and resistance you can expect. Again, think back to the Segwit and Bitcoin Cash days.
And then all of the software we use with Bitcoin has to be updated to support the new quantum-safe scheme and new address format. That goes for nodes, miners, exchanges, etc.