Prediction: Ashoka's Story
Of all the new novels Lords of the Sith interests me the most by far.
http://starwars.wikia.com/wiki/Lords_of_the_Sith
"First, as is apparent from that spectacular cover, the book features Vader and Palpatine. It also features a character who I'm not allowed to name just yet, but who appeared in The Clone Wars animated series. In terms of where it fits in the timeline, Lords of the Sith is set after the Revenge of the Sith film and before the forthcoming Rebels television show."
BUT WHO APPEARED IN THE CLONE WARS ANIMATED SERIES
This is almost definitely going to be a lead in to Ashoka being a major part in the new series OR the wrap up of her story.