To me, what makes CPython special is that it's a language interpreter that's incredibly easy to get into and hack due to its simplicity. Pypy, while probably a good standard for server use, will never have that quality to it. IMHO it would be a shame if python loses this aspect of the ecosystem.
PyPy doesn't support Python's C API. It's more of an exercise in tracing JIT compilation (and crowdfunding various experiments) rather than a CPython replacement.
Last I've looked at it, it took quite a long time to compile compared to CPython (while say luajit is not taking that much longer to compile compared to reference lua).