The very expression "centralized Bitcoin" sounds like an oxymoron to me. Decentralization was the underlying idea of the entire system, wasn't it? So, cannot be centralized because it contradicts its nature.
Should it get centralized, it would mean the system is dead...
We don't know exactly what will happen to cryptocurrency in the future as it is hard to tell but we are all aiming that cryptocurrency should be known worldwide and we are all aiming for that to happen and when that happens for sure centralization will take place.