Bandwidth mining is the next generation of crypto. Proof-of-Work algorithm is useless and pointless because it does not really provide any digital commodity. It's just a ledger. Mesh routers implemented with blockchain technology provide both a P2P ledger and a decentralized internet itself.
Mesh networks are the future of how we will transact cryptocurrenices. But that is it. Cryptocurrencies will still be secured by proof of work.
Yeah that is actually a tricky question that we are still working with. The currency needs a decentralized trusted validor. Proof-of-Work is a such validator, but there are other too.