There's a reason even the Linux dictator-for-life has been mulling over Rust. David Braben's criticism of systems-level programming languages is a fascinating read. C++ versus C is a never-ending argument; though I would tend to suggest that the 'unpredictability' of C++ when mis-used is an issue for OS programming in said language. C clearly has no shortage of bad code submissions too; and the advantages of the dictator-for-life in control of what does or does not make the Kernel is perhaps symptomatic of the language and compiler's ability to deal with crud.
One does somewhat feel that despite Linux' established base; that there is probably space for a research / hobbyist OS to be built from ground up using modern paradigms.That is, after all, precisely how Linus got started with Linux; out of desire to use the x86 chipset in full and expand a bit beyond the capabilities of other educational OS of the time (Minix being prime example). At the time, C happened to be the best compromise available between programmability and performance.