This is a real possibility, it was not long ago we could see how much gold content a paper currency was supposed to represent, this changed because it benefited the central banks but if for some reason things get out of control and central banks need to once again back their currencies with something they could choose a basket of assets instead of just backing their currency with gold, and if that is the case then bitcoin could without a doubt be one of the assets which will be used by central banks for this purpose.
I don't think so, centralized and decentralized are like oil and water, they don't mix well and there isn't any part of bitcoin that is going to be pleasing for central banks in the first place, I mean they don't like it in the first place so why get in bed with your enemy right, I would say that the best thing to happen for these two is to coexist and not combine because if that were so then central banks will eventually gain the upper hand because they are organized compared to bitcoin.