I think that in the case of Japan, many countries in the next few years will be convinced of the effectiveness of crypto-currency payments and their positive impact on the economies of the countries and will massively transfer to settlements in the crypto-currency. Doubting and neutral to the crypto-currency countries will remain very little.
I do not share your optimism. Largely positive effect of the legalization of bitcoin in Japan depends on the mentality of the Japanese. What country has officials ready to commit suicide if their reputation is tarnished? The Japanese are very law-abiding and, therefore, all the negative qualities of bitcoin will not get such a large spread as in other countries.