Some kind of microkernel, yes. With the set of required features for hardware abstraction and virtualization, with everything else being provided by the respective language runtime.
This is much faster than traditional operating system stacks, and may provide a way into bringing microkernels into mainstream OSs.
When using programming languages that come with batteries included, meaning with a good set of libraries for all the usual OS services, then removing a few layers between hardware and application helps running everything faster and increases security due to a smaller set of code.
The guys behind Microsoft's Singularity project are also researching something similar for Windows, a project named Drawbridge, where the full OS runs on a hypervisor as a set of libraries in user space.
Anyway this is nothing new, the idea of a virtualized OS goes back to OS/360, it was just kept away in the mainframe world and is now becoming mainstream.
The programming language runtime is mapped to execute directly on top of the hypervisor.
There are already such systems for Erlang, OCaml, Haskell and Java runtimes.
If the programming language has a good library, there is no need for an operating system, the hardware access can be taken care by the hypervisor.
This leads to safer and faster servers running on virtual machines.