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.
I agree with your opinion, at this time China is one of the biggest economic power in the world, China has the potential based on its economic growth and China is the worlds largest trading nation as it is the largest trade partner of the most countries in the world. With the power of their current economy, I think in the future China will be a super power country rivaling the United States