PyPy may someday be a viable replacement for CPython, but that day is not today. The viability becomes much more questionable as more and more of the Python community moves to Python 3, which PyPy basically does not support.
That's not the point. The point is that the argument that modern languages are written in or depend on C/C++ is fallacious: there is no need for C or C++ there, nor is there any technical advantage to their use. CMUCL and SBCL are almost entirely self-hosted, and things like PyPy and JikesRVM stand as strong examples in other languages.
Nobody here has said that C or C++ are absolutely needed. I merely pointed out the reality of the current situation, which is that both C and C++ make up a big part of basically any web app around today, even those written in some other popular languages.
Also note that I referred to "the most widely used" implementations of those languages. Yes, we know that PyPy exists, but CPython is still used far, far more often. Yes, we know about Common Lisp implementations like those you listed, but the reality is that they basically aren't used in practice. PyPy, CMUCL and SBCL are essentially irrelevant when considering the big picture. C and C++ are involved in one way or another in pretty much every other case.
If you refer to the original post in this thread, you will see that it was about the supposed unsuitability of C++ for web development. When we look at the entire picture, however, we do see that such sentiment is quite wrong. C and C++ play an absolutely huge role in modern web development and web applications, regardless of what some people may think.
