Some of the Hinterlands characters may pop up again! We plan on having a little episode where P returns there for some unfinished business if some conditions were met. The conditions are a bit complicated, though, so only people who really explored them should get this little adventure.
Greta is likely to make a return later in the game too. Who knows what she will be up to, though!
Some of the other characters may return, we will see. Not all, but a few.