Only one I can see returning is the Grimm troupe with the grimmchild as the troupe master
Quarrel as others have mentions, is dead.
Isselda and Cornifer showed no interest of venturing outside of Hallownest, and Cornifer specifically retired at the end of the game
The Hunter is also in retirement (and old as hell). He gave the journal to the knight so that he could finish where the hunter started and based of dialog, the hunter seems older than ELDERbug based off his recollection of the events of Hallownest and speaking about the Pale king with such knowledge, so there is a chance the hunter is dead as well.
