Since Chinese President Xi Jinping has publicly supported the blockchain, it can be expected that China’s share will become even bigger. It will be one of the ways to control technology in the absence of competitors from the United States.
China as a country doesn't have any share of bitcoin's mining to increase or decrease in the future. it is only individuals and companies that are mostly outside of China and many are even in US and are connecting to a Chinese pool the server of which is both inside and outside China.
as for the government "support" they have never supported bitcoin or even the blockchain technology. they have only hyped up their future plans about releasing the "new" version of their national fiat which will probably be called Digital Yuan.