The Bitcoin miners will never move to POS unless countries around the world aggressively move to shutdown any mining operations. That seems unlikely especially when governments are actually starting to take part in mining... If we could get to the point where POW mining could be done by anyone with some spare CPU instead of high power ASIC or GPU then it would become a lot more decentralised. BTC mining could become the most popular screensaver ever... But miners wouldn't vote to make mining ASIC and GPU proof. And we would still have farms of CPUs mining but hopefully drowned out by billions of consumer owned CPUs...
POS mining send great but unless it can support a very large pool of block creators or witnesses has the same centralisation issue. Chains like GridCoin randomly let anyone be a block producer based on a probability related to how many coins you hold. But again we have centralisation as the richest will get to do the most staking.
So far the only truly decentralised system I've seen is that used by directed graphs such as Tangle in IOTA. Everyone participates approving transactions and doing a small amount of work to avoid spamming. However so far I think Tangle has some issues that mean it is not to be trusted. Yet. Until then I think the best hope is a chain using POS with a large and community elected set of block producers. Vitalik claims Casper can use up to 2000 but I don't know if that scales to use for all blocks Vs the occasional checkpoint blocks.