Let's rather look at the other side of the coin, when the Chinese miners gets shutdown by their government. We will suddenly see a massive drop in the hashing power and more people with smaller mining rigs would be able to re-enter the mining scene from all over the world and it will be even more decentralized when the difficulty drops.
We currently have loads of people mining Alt coins, because their mining rigs are too small to compete with the high difficulty and hashing requirements for mining Bitcoin, so if this difficulty drops.. those Alt coin miners will start mining Bitcoin again.
The Chinese government would do the rest of the mining community a huge favor, if they shut their own miners down.
Also, some of those miners will quickly relocate to other countries to be able to continue mining or they will sell their ASICs on the black markets.
Most of my worries come from them taking over and changing how supply works or imposing new, arbitrary rules like BCH causing the main Bitcoin community to split again.
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I'm not going to argue here if the Chinese government is to be trusted or not - that's something you decide for yourself. What I want to know, is to what extent are they going to allow Bitcoin to remain independent when it becomes harder to turn a profit and how "independent" these mining groups are from the influence of the government.
No, it's not doomed to be centralized in China.
Scenario 1:
The government will take over and continue to mine most bitcoin. They still cannot keep it to themselves because they have to cover mining operation related expenses. They have to sell/trade it somewhere and they cannot prevent anyone who bought from them to send it anywhere else in the world.
Scenario 2:
The government will take over the mining farms and shut it down. Bitcoin will still thrive since anyone or any group can set up their own equipment and start mining bitcoin unless if they are in countries where it's forbidden by their law to mine.
I guess time will tell, hopefully, we get new security measures in the future for cases like this. I'm still bullish on Bitcoin because its the only asset worthwhile having in this current world situation but I can't run on hopium and people expecting an authoritarian government to play things smart instead of forcing themselves in like they are used to. I think a BCH like scenario is more probable rather than a complete overtake scenario like Steem's and Justin Sun zeroing out people but I guess time will tell. I just hope we are ready to fight back if that's the case, there's no jumping off this ship now :-D