Despite this league's steep growth in the past three years, I'd say the stadium situation is still one of the biggest concerns. Considering the J league (football) will follow the same system as the other european football leagues, a lot of these stadiums won't have the same availability as they do right now. Sharing stadiums will be harder
Theirs at least one new one coming. The Rugby stadium near Meiji Jingu stadium is being demolish, the new baseball field will be built on the Rigby stadiums site, while a new Rugby stadium with be built on the old baseball field.
Although Japan would never win a World Cup, they are still the top-ranked nation in Asia, winning the Asian Championship 25 times. They can occasionally win against some of the rugby-mad nations such as Georgia, Fiji, Tonga and Samoa, and have upset top nations including South Africa, Ireland, Wales and Scotland over the last decade. So I wouldn't call Japan "not successful". Also, rugby will never surpass baseball or soccer in terms of popularity in Japan, high school rugby has quite a huge following, which their final goal is to win in Hanazono (like Koshien for high school baseball).
I'd probably argue that the NHK Spring Mitsuzawa Football Stadium would be the best place to play in, should you be the unfortunate recipient of a hospital pass...
