They won't, and they won't come close. A few basic considerations here: Japan isn't the biggest market for MMA, and the best MMA fighters don't live in or near Japan. Creating a situation where the majority of the best fighters travel around the world to fight in Japan just doesn't make any sense from a logistics perspective. MMA in North America (UFC, to a lesser extent Bellator) and Europe is going to have an audience. One has an audience. There isn't room there for Rizin to become the top org.