I think we need hardware support first before we can think of any language. The support has to be transparent to any other part of the system. On the top of that the language that you are using has to be memory safe. This is probably where C falls off.

Yes, microkernels and hybrid kernels too. Yet Linux/FreeBSD/Random Unix Clone are monolithic.

It is the time for a new safer kernel! :)

http://en.wikipedia.org/wiki/Hybrid_kernel#NT_kernel