Outside of planning on returning to the galaxy far, far away again in the future, Fisher also according to IndieWire just days ago agreed to create a sequel to her one-woman stand up show, book, and eventual broadway play Wishful Thinking that would have been titled Wishful Drinking Strikes Back: From Star Wars to, uh, Star Wars!
The news that Leia, and potentially the Resistance, are currently set to have a larger role in Episode 8 makes sense given the way events unfolded in The Force Awakens.
With control of the galaxy hanging in the balance, it only makes sense for Leia to be front and center, doing everything she can to bring peace and freedom to the galaxy.
Now that she has passed, it is unclear if the sequel will move forward at all, but it shows that Fisher had no plans in slowing down.