The difference in energy efficiency between PoS and PoW is at least questionable...
If we assume that both types of cryptocurrencies are to be secured to the same degree (electricity cost is replaced with equal capital cost).
If I am able to comprehend non-trivial economic issues correctly, the energy expenditure will be only slightly delayed, not diminished.
That energy expenditure may be actually reduced one day, but only if a typical home heater will be able to mine cryptocurrency...
This would also end the nonsense of non-mining nodes as all nodes could be staking nodes
If you do not run a validating node, how do you know you're connected to honest nodes?
If you have any ideas how to avoid taking control over blockchains by economical mammoths, please reply.
Control over PoW blockchain is just a choice between the correct blockchain states (all outputs and inputs must match).
And in practice, that is very expensive and temporary control.
But my answer could be Elastos (and its sidechains, which can be PoW or dPoS).
Elastos mining is merged with Bitcoin mining, borrowing from Bitcoin its unparalleled security.
Potential attacker must dispose at the same time majority of Bitcoin's hash power and votes in dPoS layer.