There are safe languages that are similar enough to C that it is not hard to pick them up for a C programmer. I agree if the replacement is ML or Haskell. But e.g. Rust, Cyclone, or Go (if a GC is acceptable) are not going to be hard for most C programmers.

Also keep in mind that most of the "safe" languages depend on runtime which isn't written in a safe language.

Rust is almost runtime-less. The Go runtime is mostly Go since 1.4.

This is also true for C - there's some stuff in every C standard library that has to be written in asm, once for each supported platform.

I didn't say it's not going to be work :).

So you're just pushing the problem somewhere else. [...] So the bottom line is: there's always something underneath.

That does not mean that, say, Haskell is not tremendously much safer than C. First, because you only have to implement the icky parts once. Second, because a better type system and abolishment of undefined behaviour gives you more safety for a very small cost (if at all, the extra compile time for a better type system is probably negated by the cost of headers).