Could nonvolatile RAM replace a computer's file system?

Citing a rumor that upcoming Macs may offer a 512GB RAM option, a user imagines a machine that ditches main memory, makes RAM nonvolatile and replaces the file system with in-memory data. They suggest excess data could spill to the cloud, and speculate that the design could simplify software, avoid disk roundtrips and deliver 100x throughput without caching. They also call the undertaking a herculean effort and say nonvolatile RAM would have drawbacks.