I believe that the centralization of bitcoin you are mentioning will not happen again in the future because electronics manufacturing companies like samsung are starting to develop hardwares that are use exclusively for mining. It will make the whole network more decentralized and powerful when it comes to processing transactions leaving the hashrate for china be in minimal.
In that case, then Bitcoin mining would be decentralized like it used to be within its early days. Competition is needed to eliminate the occurrence of a monopoly (in this case Bitmain). If Samsung gets into the game, then I believe that mining hashrate would be greater in different geographical areas of the world.
Another thing that Bitcoin would need to improve would be its distribution of nodes across the world. Recent studies around the web, have shown that a huge percentage of Bitcoin nodes rely on data centers while Ethereum has more geographical distribution than Bitcoin. In this sense, Bitcoin is more centralized than Ethereum since most nodes are not widely distributed. Perhaps, in the future, this would no long become an issue as people across the world start setting up full nodes to help support the network.
I guess that if Bitcoin would've had a rewarding model like Dash and ZenCash, many people would be running nodes to support the cryptocurrency's network. However, since there's no incentive to run a Bitcoin full node, people would think twice before doing such task.
Nevertheless, only time will tell us what lies ahead for Bitcoin's decentralization. If the community involved acts against measures that will further centralize the cryptocurrency, then Bitcoin will continue to prevail for years to come. Just my thoughts