[wilsonthewhale]

It's more likely for these systems to slowly evolve into something new rather than being replaced entirely.

MacOS and Linux, at some level, are already very, very different than earlier unix systems. The BSD's are more conservative, but there's still systems being reworked across all of them (HAMMER in Dragonfly, pledge/unveil in openbsd, etc.). The ideas of unix will probably be with us forever, but the precise details of implementation are transient.

[ghaff]

I suppose one could imagine something related to dataflow architectures, for example. But history still suggests betting on something that is an offshoot/evolution of basically all the mainstream operating systems we have today rather than a radical ground-up rethink.