I would like to see more sector's of the galaxy explored in more depth. I know it won't happen until the new movie and show are out, but I really liked The Lords of Nal Hutta and Suns of Fortune. Some thoughts: a book on the Corporate Sector or Arkanis Sector. Another more focused option might be a planet book for Coruscant. An adventure book to go with Rise of the Separatists, Collapse of the Republic, and Dawn of Rebellion would also be nice. If its good I'll take more gadgets and gear, etc.

What is most likely is the aforementioned vehicle collection book (I'm partial to the title "Starships & Speeders but that is not here nor there).

What I would like to see instead is not an era specific book, but perhaps some sort of set of alternative mechanics for important things of Star Wars spread out over the different sourcebooks, such as plotting new hyperspace routes, crafting rules for gear, ships, mass combat and the like in one book. I'm sure it will never happen cuz money,but it would be nice to see the small additions for the rulesets expanded on in a singular book to make life easier for GMs and more interesting for players.