What's next: PMI-ACP or PMI-PBA or...?

I think PBA is a specialising level you will need either you are waterfall or agile. I am thinking about the same now, to go for my PBA and then later ACP. I am very much a waterfall driven.

Well, as I mentioned I have both and I mentioned my reasons. In my personal work experience I have been involved (and I am still involved) in initiatives regarding both worlds: agile and business analysis. About agile I started working in the software field but after that (from 1995) I have been working on agile applied to the whole organization (is the way agile was born in 1990 as a formal definition). The PMI-ACP is still software oriented no matter the methods you need to learn and understanding to get the certification becomes in the last years to agile solution delivery methods (DSDM and SCRUM for example). About business analysis, while I have the IIBA certification too, I think the PMI is making a great work and in my personal opinion is the role that is growing faster because the business world dynamic. I hope (at this time is what you can see in the PMI products) the PMI will put some clarification about the role with all the products the PMI is delivering at this time. If you ask to me, I would go for PMI-PBA.