Another way to visualize it is to examine the fields covered:
We can start off with the field of Project Management
 

 
Mostly contained within this Project Management field is the PMI’s world view of project management that I am calling  PMBOK v4 GuideTM content.


This PMBOK v4 Guide content is not a pure subset of project management however, since things like the Code of Ethics, while good properties for a PM, are not strictly project management. Likewise there are many project management techniques, like the Theory of Constraints, that are not full embraced by the PMBOK Guide.

 
When we add Agile and Lean principles to the mix we see a big overlap.

 
Agile and Lean are just as concerned with Quality and Estimation as the PMBOK Guide, but their approach towards it is often quite different.

The last major body of knowledge is Leadership.

 
Leadership covers topics like Visioning, Ethics, EI, Situational Leadership and Servant Leadership. Many of the concepts Agile projects employ.  It is the combination of these fields Project Management, Agile, and Leadership that forms the basis for the Agile Certified Practitioner exam. Shown by the dotted red oval below.

 
In this model we can map all of the Knowledge and Skills (KS) and Tools and Techniques (TT) that will make up the exam, but the picture gets crowded pretty soon, so this is a partial view.
   

Anyway, hopefully the box model and the Venn diagram provide useful ways of understanding the content. The official PMI announcements about the timeline come out on Monday May 16. As always, I welcome your questions and comments.