Mining centralization is done by China already..
90% of BTC transactions are from China...
Who ever said Bitcoin is decentralized? Only the development process is decentralized.
Contrary to popular beliefs, most Bitcoin transactions are likely not to originate from China. I would say that the general public would have a certain degree of difficulty using it especially since their government has restricted Bitcoin there and it isn't recognised as a currency by the central banks.
Mining is also not extremely centralised in China, at least not to the extent of 90%, possibly around 50% of the mining rigs are in China. It is rather inaccurate to estimate it based on the pools since miners can always connect their machines to Chinese pools due to their location and/or fees.
Bitcoin software is decentralised since it does allow the community to decide what modifications they want to make for it to be considered Bitcoin. Anyone can change the code and people can choose to use and recognise it as the official Bitcoin.