From the point of view of the development of blockchain and cryptocurrencies, Japan will become a super power, not China. Japan has already legalized cryptocurrencies and attracts investors from all over the world.
China has been focusing on its own production and reducing the amount of imports to a greater extent possible. This rise in their own production has given an upward push to their GDP and china has the huge market in the Asia right now. Besides, as the country is now completely labor and capital efficient, China has started spreading its investments in foreign countries and moving Chinese to the foreign offices which further improve the GDP.