A safer variant wouldn't be C. What makes C great for OS development is that it is just a step above assembly and you as a developer are given tremendous amount of power to do good and evil. C#/Java are programming languages with training wheels and it's great for application development. But for low level coding required for OS, network stacks, databases, etc, you really have to take the training wheels off.
I suppose you can try and make the C type system more stringent, but then it wouldn't be C. And considering they are aiming for backwards compatibility with existing C and its immense code infrastructure, they will have to keep the "flaws" in c for all.
Time would be better spent making the libraries/kernel/etc sturdier but if they can pull it off and win the hearts and minds of OS developers, then so be it.
Also, people have been trying to sideline C for decades. Each attempt has only reinforced C's standing and reminded us why C is so essential for OS development. Anyone remember the ill-fated attempt by Sun with their JVM centered JavaOS?