Proof-of-Stake(POS) is still theoretical at this stage, there is no working solution or proof-of-concept. It is a nice(ish) idea to reduce the energy consumption of blockchains but isnt really a solution to decentralisation.
There are some working solutions now, like NEO, Dash, and NXT. Ethereum is sure to adopt it as well; a lot of details are TBD but there's little question that the community will adopt some form of PoS.
I'm not saying it's perfect -- there are some downsides like needing a cap on fork distance in order to prevent stake bleeding attacks [1] -- but it's certainly viable.
