As an embedded programmer, it is still very hard to displace C and will be for some time. The two main reasons: the compilers are well-behaved, and the debug tools are very, very mature. One thing newcomers overlook is the importance of understanding what the compiler does to the code. C++ is notorious for being painfully unpredictable, and in the embedded world, that is a death sentence. mbed is learning this the hard way. On the other side, debug tools are critical. Unlike the decade long surge of web-related programming with its sophisticated GUI-based debugging, embedded is a completely different beast, and requires much more attention to detail since reprogramming costs are so high. Because C has such a robust hardware debugging ecosystem, it is a clear winner.

It'll be a long time before anything knocks C down as #1 in the embedded space. Even as the definition of embedded stretches to include *nix variants (like Yocto), there will always be the squeeze to get rid of that and run bare metal with C.