Most people would have said that this would never happen. Visa is opening up its payment processing system directly to qualified third-party developers. Visa Developer has 150 different APIs to access Visa systems, from simple Visa Checkout and Visa Direct, to more complex solutions things like Visa’s location, foreign exchange, and tokenization services. With services like Apple Pay gaining traction, this is seen as an effort to maintain Visa’s relevance.
The “network effect” is an economics term that basically means a thing becomes more valuable the more people that use it. If Visa can stay on the development radar, it should be able to maintain it’s market dominance. You can read more about the recent announcement here.