PoS won't reduce gas fees, but subsequent network upgrades will. Sharding is one of the most anticipated scaling techniques that will reduce gas fees and increase transaction throughput on the main chain by a long shot. Even though ETH by itself will become cheaper and faster than ever, Layer-2 networks will still be useful for micropayments and other sorts of things. They won't go away, because such networks will always be cheaper and faster to use than the main chain itself. The same can be said about Bitcoin's Lightning Network. Besides, the Blockchain will always be prone to congestion no matter how scalable it becomes. Off-chain scaling solutions help bring the masses into the world of crypto, so they will be with us for a long, long time. Just my thoughts