Researchers from the Russian Quantum Center suggested that quantum computing could eventually obsolete blockchain altogether.

"Within ten years, quantum computers will be able to calculate the one-way functions, including blockchains, that are used to secure the Internet and financial transactions. Widely deployed one-way encryption will instantly become obsolete." https://www.nature.com/articles/d41586-018-07449-z

Quantum computers put blockchain security at risk - Bitcoin and other cryptocurrencies will founder unless they integrate quantum technologies, warn Aleksey K. Fedorov, Evgeniy O. Kiktenko and Alexander I. Lvovsky.