Nothing will make bitcoin to be centralized, it will be decentralized, bitcoin is just like gold, but digital, even if the banks are holding the greatest amounts, it is people demanding and selling rates that will determine the price. But, in some aspect, it could be centralized, like governments having policies that any one having bitcoin to be paying certain monthly or annual amoumt. Goverments will try to manipulate and make people depend on them to be able to buy and sell bitcoin so looking for more ways to further centralized the coin. But with what I am looking in my view and perspective, I do not think bitcoin can be centralized in term of price because the price will never ever be controlled by centralized bodies which are the governments, bitcoin is decentralized beyond that.