> You already broke backwards compatibility once in beta1

There is one other thing to consider, that is projects with pinned dependencies will have to upgrade to the last Cython and update their generated sources if we don't do the renaming. I don't know how often this happens (for example, Python3.7 changed the result of PyUnicode_AsUTF8AndSize() and PyUnicode_AsUTF8() to type const char * rather of char * and that is backward incompatible if you compile with a C++ compiler or with -Werror) but certainly is worth to consider.

Also, take into account that beta period is precisely the moment to fix these kinds of problems (although I apologize for any inconvenience this may have caused).