Rules-wise, we're probably going to see a lot of overlap between F&D and the other two books.
At the very least, I suspect we'll see the five Force Powers (Enhance, Foresee, Influence, Move, and Sense) get reprinted in F&D, with the possibility of others. Naturally we're bound to see a fair number of talents get reprinted, especially if F&D was written to also cover non-Force using characters as some have suggested might be a possibility. AoR didn't have that many new talents when the Beta came out, and the core rulebook's only added a small number of newer ones (which where covered in the weekly updates anyway).
For species, Humans are a given, and we might see others from prior books show up in F&D as well; just because this is the book that pulls the curtain back on higher-end Force users doesn't mean that each species has to be one that's had a Jedi representative in the films or EU. I know that folks have been hankering for Togruta, Zabraks, Caamasi, Cereans, Kel Dor, and Miraluka, but there's not guarentee that even half of those species will show up in F&D, and FFG could very well recycle species like the Twi'leks (EotE core) or Sullustans (AoR core) or even droids (if F&D does permit for non-F/S PCs).
A lot of the equipment chapter's is bound to be recognizable to folks with either of the other two core rulebooks, though we're likely to at least get a few new options seeing as how the Force user crowd have a preference for close-quarters weapons, with things such as short lightsabers (at least regular shoto if not the guard shoto) and dual-bladed lightsabers being likely candidates.
As happened before, I suspect there will be a lot of complaining and gnashing of teeth from a portion of the customer base about having to buy multiple core rulebooks with a bulk of repeated material in order to get a "complete" game, just as there was when the product line was announced and FFG made their "three rulebooks" approach known.