Yours is an interesting article, but you should be aware that there is a whole field of study called Quantum Cryptography, which deals precisely with cryptographic algorithms suitable for quantum computation. Also, regarding the blockchain, I know of at least one cryptocurrency which is designed precisely to be resistant to quantum brute force, which is QRL (Quantum Resistant Ledger, see the website https://theqrl.org/). So, although it is certainly an issue for the whole blockchain technology, it is not in any way unfeasible to be handled.