After starting to write a small llvm-based language in C++ (before going back to Haskell), I had already dependencies on LLVM, xdg-basedir, log4cxx and doxygen in my build system. I was using the system libraries, and thinking all the time that it was good this was only a side project, because it was really a terrible way of managing dependencies.

As for Rust replacing Ruby, why not? It is a general-purpose language, it eschews a lot of the C/C++ verbosity, lack of memory safety and weak typing which make them such a pain. I could see it easily as a strong contender in the web platform department once it matures.