Posted in a different thread, but my thoughts on what we'll see for careers would be along these lines...
There's going to be at least one Jedi career in the book, as Jedi are a huge part of Star Wars to the point of being one of it's most distinct and recognizable elements. Fanboyism of Han Solo or Boba Fett aside, when folks think of Star Wars, Jedi are one of the top things to come to mind, particularly in light of the recent The Clone Wars series and it's heavy focus on Jedi characters.
If it's just the single Jedi career, then expect to see the initial three specializations to be Consular, Guardian, and Sentinel. Like 'em or hate 'em, those three tags have become a fairly-well known shorthand for "scholarly/mystic Jedi", "combat-focused Jedi", and "sneaky/investigative" Jedi respectively.
While it's not impossible that FFG could break Consular, Guardian, and Sentinel out into three separate careers, I kinda hope they don't. Having a single Jedi career, particularly for the Rebellion Era in which this book will be set, makes more sense, and leaves more room for other career and specialization types. At most, we might see two Jedi careers, going along the Consular/Guardian split in a way similar to how the SW:TOR MMO handles it.
I think the type of Force-centric career we're like to see more than one of is non-Jedi Force user, being split into (for lack of better terms) a Force Adept (focused more on the mystical side of things) and the Force Warrior (using the Force in a more direct and/or physical method), with specializations quite easily drawing from existing Force Traditions (of which there are many to pick from, each with their own themes).
Since this is going to be a stand-alone rulebook and not a glorified supplement (which is the route that White Wolf took with their New World of Darkness line, having a single corebook and each supernatural type requiring a separate source book), the FFG design team is going to need to address playing non-Force users in a Force & Destiny campaign (if nothing else to allow for Droid PCs, who thanks to Artoo, Threepio, and HK-47 are semi-popular character types). It's possible they could just cherry pick from AoR and EotE, but I've got faith that we're going to get new careers and mostly new specs (probably safe to assume there will likely be at least a couple repeated specs, much as AoR had repeats of EotE specs).
Now that I'm thinking about, I'd really prefer to see an even split in terms of careers between Force-users and mundanes, with the mundanes simply being akin to "galactic adventurers" instead of being beholden to a shady past (EotE) or part of a larger organization (AoR).
I'll go a step further and say that at most I hope FFG doesn't go beyond 2 Force-centric Careers in Force and Destiny with the remaining 4 being "mundanes" (whatever that means).
I played D20 Star Wars for **** near a decade. It was great, but it had a ton of flaws--not the least of which was its ridiculous devotion to Jedi Consulars, Jedi Guardians, Jedi Sentinels, Jedi Aces, Jedi Healers, Jedi Scholars, Jedi Investigators, Jedi Masters, etc., etc., ad nauseum.
The Saga Edition tried to remedy this by streamlining the game, but still fell prey to "crunch addiction" with every expansion. FFG has a good thing going--they have a system that captures Star Wars and the setting **** near perfectly. I'd hate to see it ruined by a book that unveils 18 different "types" of Jedi.
There's arguably only a couple "types" of Jedi--those that study the Force (Consulars) and those that use the Force to protect others (Guardians). Sentinel is largely a made-up type that was used to provide balance in the original Knights of the Old Republic game. It's not needed in the slightest.
I hope they don't have any force using careers. I hope they are just more force using specializations and none of the careers say Jedi. As being a jedi is a role playing thing. Not a set of abilities. They have training in the force. but no 2 jedi are the same. There are some commonalities that many have.