Its not at all premature to be asking this 🙂
We are porting L4 which is a microkernel. We anticipate that other microkernels will also be ported.
There Are a couple of new opportunities too:
Even if you have a monolithic kernel, you can start to adopt finer-grained isolation on the Mill and become more microkernel-like, or even split up user apps into services.
There is also the exciting possibility to keep isolation without actually going via syscalls for IPC: with the Mill, you can build a new kind of OS where calls between clients and servers – or peers – goes straight across in the same thread via portals. However, this challenges how a lot of conventional OSes think about thread to process/task mappings and what kill() does and preemption and time sharing accounting and so on. So an exciting future research area!
Classic monolithic and micro- kernels will run as-is on the Mill architecture and run very well. The Mill allows for a evolutionary migration to greater isolation too. But the Mill also makes technical room for new innovation and experimentation 🙂