Thats then probably for the renewal as well as conversion no?
I would think that that would be exclusively for the conversion to an SA PPL, NOT for the renewal of your FAA PPL. After all, once you have that SA PPL, you're going to use that as the entry for the SA CPL. You don't need the FAA PPL for that anymore. And since the 15 hours is probably all dual, you won't need the FAA PPL to exercise PIC privileges either.
Ok one more question. Is a CAA CPL or JAA CPL better?
FAA, JAA or SA CPL? It all depends on what/where you want to fly eventually.
Particularly if you want to fly commercially (maybe even with an ATPL in the future), in principle your license has to match the registration of the aircraft. Only within JAA land do you have the ability to mix&match. But there are exceptions to this, and exceptions to the exceptions. If you think converting from one PPL to another is confusing, try converting an ATPL (CPL+IR+ME+MCC+TR) into another, or flying commercially on a "rendered valid" foreign ATPL!
This is getting outside the realms of "private flying" though. If you want details on CPL level or higher, may I suggest you post a question in the "professional studies" forum?