It is a great start (and certainly feels like the natural matriculation) but I know that many Ph.D PP programs require one year of intense economic theory and one year of calculus. I don't know if those will be built into your MPA, but if not, some school offer provisional acceptance without the econ/calc and then you can enroll up to 12 months later once you have completed those requirements.
This is the same route I am planning on taking and the MPA I am looking at doesn't include those requirements. Hope this helps.