[pjmlp]

Yeah, but we are still far off making it mainstream beyond some key use cases, QNX, INTEGRITY, language runtimes on top of type 1 hypervisors, all kernel extension points being pushed into userspace across Apple,Google,Microsoft offerings, Nintendo Switch,....

[bcrl]

Given the tectonic shift in priorities for Linux kernel development over the past decade, I'm willing to bet that many key developers would be open to a microkernel architecture now than ~25+ years ago. CPUs now have hardware features that reduce the overhead of MMU context changes which gets rid of a significant part of the cost of having isolated address spaces to contain code. The Meltdown and Spectre attacks really forced the security issue to the point where major performance costs to improve security became acceptable in a way that was not the case in the '90s or '00s.