Re-file under "You don't fucking say?" If you're going into something planning to do a trilogy, you'd damn well better know what the endgame is for the whole arc before you start plotting book one of the series. Even if you're planning on "subverting expectations" from prior work, you still need to know what the final chapter of the whole thing looks like so you can maintain internal consistency in the narrative across multiple sections of the story. Only a hack goes into trying to build a story without having some idea of where it's going to go, because otherwise you end up with a meandering, meaningless storyline that ends up being less than fulfilling for the reader/viewer.

If KK hadn't thrown the baby out with the bathwater on the EU, and Disney had just sucked it up and paid the writers the royalties like they should have, they could have had the perfect followup trilogies from Zahn's books. Granted, the would have either had to have made them animated (since the original crew had long since out-aged the time frame of the books) or re-cast the parts with a younger set of actors, but the Thrawn series pretty much IS the sequel in most fan's minds.