I wouldn't worry about the tradition. I think the fact that it was not easy for a Japanese athlete to become a Yokozuna means that the international competition is strong, the popularity of sumo goes well beyond Japanese borders. It is a little bit easier to follow sumo tournaments now when NHK World broadcasts 30 minute long "Sumo highlights" shows during championships. (It is quite recent, just a few months ago there was no way to follow championships)