SOA promises composite applications that closely model the way organization do business -- that is SOA promises reusable buinsess services. That is great.
In my view POA (or some variant of the acronym) will take hold soon after. What are the key elements of POA. Composition of business services into "Practices" -- goal oriented composite business processes. POA relies on a combination of proven business services that together form -- Practices. Practice is a polished set of business services that have been perfected or almost "evolved" as a result of various business activities. It also focuses on goal orientation rather then compositions. Meaning that the architecture will promote evolution of practices from so so to good to better to best. Obvious questions would be "how do you measure good, better, best"? I dont have an answer, but working on it :) -- maybe by revenue, customer loyalty, or some other key business metric.
You might say, "How is it different from BPM?" Well, in my view BPM still falls into SOA space and does not address the questions of how composite business services form into "Practices", how do you consistently improve and integrate composite business practices. Practice to me is a discipline that lets companies excel at what they do. SOA will let them integrate, POA will let them take to the next level.
The new discipline will have to focus on how to create, improve and deploy best of breed goal oriented processes that can almost self evolve.
Or may be, I just like new acronyms. :)