I think this will happen in the nearest two years. And maybe VISA will make this happen, by the way. If it will invest in this technology and integrate it in its transactions system.
There could be a possibility that VISA might adopt Blockchain for its own benefit someday. In the event Blockchain technology becomes so successful, VISA would take the right direction towards preserving its business model by integrating Blockchain into its platform. However, if VISA doesn't adopt the Blockchain, then I'm afraid that it'll eventually be replaced by it. One thing for sure, is that Blockchain is improving at a fast pace. Which means, that sooner or later, Blockchain would scale to millions of users without sacrificing speeds or even costs at all.
With the advent of innovative technologies and consensus algorithms (such as DAGs, ZK-SNARKS, etc), Blockchain has enormous potential to take the financial world by storm. Of course, for Blockchain to beat VISA, it would need to become regulatory compliant (something that has been quite of a struggle lately). However, if Blockchain manages to gain full compliance, then there's nothing stopping it from beating VISA. Just my thoughts
