eth2 (which is more than just proof of stake) aims to substantially reduce the fees by allowing the network to scale up (I think the current target is 100,000 transactions a second). This is partly enabled by proof of stake and partly enabled by other stuff like sharding.
Eth2.0 is actually filed under things_that_are_very_hard_to_research_develop_and_deploy_to_production_as_they_are_currently_supporting_a_200_billion_market.txt