> Why does anything need to replace C? It's been fine for years and still does exactly what it needs to do.

well, for one the h/w model for one has far progressed beyond what the state of the art was during C's genesis. for example with the advent of multicore machines trying to use C's facilities to exploit available h/w resources becomes quickly unwieldy. witness the rise of event based approaches f.e. libevent and friends, or the rise of lockfree mechanisms etc. etc.