Bitcoin can't do as many transactions as Visa right now? Why weren't we informed of this sooner? I can imagine there will be solutions. Whether they arrive quick enough before the universe explodes in a supernova of bitching is another matter.
I don't get why everyone is always worked up about this either. Comparing Bitcoin at its current size and and stage of development to VISA is like comparing a mom and pop burger shop to a chain like Mc Donalds.
The owners worrying about how they will scale to open 1000's of locations and serve billions of burgers is not likely going to help them in the short term. Instead, by concentrating on what they do well, serving superior food, (not hard considering the competition), a friendly atmosphere and great customer service will allow them to grow at a healthy rate and keep everyone happy.
The same is true with Bitcoin. No need to wonder how they will compete with Visa when they are only the size of a small bank. What they need to do is keep offering benefits the banks or VISA network don't offer and continue to refine those. The growth will come on its own and the scaling can be implemented incrementally as it does.