As you may already be aware, Hollow Knight developer Team Cherry is currently hard at work on a sequel called Hollow Knight: Silksong. We know that Switch will be the only console to receive the game at launch, but other details are still pretty slim at present.
Changing that slightly, though, the team has provided a quick update on the game,
in a recent interview, William Pellen, the co-founder of Team Cherry, was asked if they had plans to include past characters from Hollow Knight in their highly awaited sequel to Hollow Knight, Silksong. This is what he had to say: “We actually do have some plans for having Quirrel appear at some point in the game, kind of a secret for dedicated players to find.”
As another tidbit of information he also provided as the information that the final boss will infact be Menderbug.