I am not an expert in this matter but from what I understand and things that I have read, as long as you can pool the work for mining somehow it will end up becoming what you can call "centralized".
It is in my opinion that bitcoin's PoW will shift to PoS or some protocol similar to it.
it is highly unlikely.
you can add a lot of tiny little features to bitcoin as much as you like but making a big change which is requiring a consensus is not going to be easy or even possible.
as Satoshi has said "The nature of Bitcoin is such that once version 0.1 was released, the core design was set in stone for the rest of its lifetime."