The API leaking all implementation details will remain available as an opt-in option for Cython, cffi and debug tools. But this API will only be usable on the "slow" Python runtime, the one which keeps maximum backward compatibility. To get new optimizations, you have to use Py_INCREF() and avoid accessing C strucuture fields, which may or may not need to modify your code.
Hum, please, join the capi-sig mailing list, since I already explained that in my long reply to Stefan on capi-sig ;-)
Interesting. I didn’t know that list exists. I’ll respond to your message on that list.