JK Rowling has hinted the character Albus Dumbledore will feature in future films in the Fantastic Beasts and Where to Find Them series.
The author has already revealed she has planned scripts for a total of five movies in the franchise, the first of which is released next month.
Speaking about the film at a fan event in London, Rowling said: "We do talk about Dumbledore and Grindelwald."
It is not known who would play the role of Dumbledore in future films.
Richard Harris, who died in 2002, and Michael Gambon have previously portrayed the character in the Harry Potter films.
Speaking at the same event, director David Yates said: "We can't tell you too because we'd have to kill you all, but we do mention Dumbledore and he features in a wonderful scene between Colin [Farrell] and Eddie [Redmayne].
"Grindelwald does feature in the background and is going to become a much more prominent feature moving forward," he added.
In the stories, Dumbledore and Grindelwald were best friends but their relationship broke down decades before the events of the first Harry Potter book.
Rowling has previously spoken about the close relationship between the pair, adding the Hogwarts headmaster, who she confirmed is gay, was once had romantic feelings for the dark wizard.
Fantastic Beasts and Where to Find Them is a prequel to the Harry Potter series, set 70 years before the first book and film.
Analysis by Entertainment correspondent Lizo Mzimba
The news that J K Rowling is "pretty sure" that the Fantastic Beasts and Where To Find Them film series will expand to five movies is welcome news for fans of Harry Potter, but even better news for the studio that will produce and distribute the new films - Warner Bros.
For a decade the studio had a string of hits with the eight Harry Potter movies. At the time they made up the biggest franchise in cinema history. The series has now been overtaken by Disney's Marvel Cinematic Universe (MCU), thanks to the billion dollar box-office of films like The Avengers movies, Iron Man 3 and Captain America: Civil War.
Warner Bros has tried to emulate the success of the MCU, kicking off with Batman v Superman: Dawn of Justice. It is planning several more films featuring those and other DC characters like Wonder Woman, Aquaman and The Flash in a DC Extended Universe series of movies.
Financially the hugely expensive DC films have so far generally not performed at the same level as many of the Marvel movies, and won't have delivered the huge profits Warners will have been hoping for. And critically, a significant number of negative reviews could lead to a diminishing, rather than rising box office in the future.
Conversely, the Potter series still enjoys a massively enthusiastic fanbase.
The first two films in the Fantastic Beasts series (which comes from the Potter universe) will have David Yates (director of the last four Potter films) behind the camera. Potter producer David Heyman is likely to produce all five movies, and perhaps most importantly the series will be written by JK Rowling.
Together they're a team that is perceived to have delivered exactly what audiences want on the big screen, and crucially what Warner Bros needs and expects at the box office. Five new films from such a proven team is a massive boost for the studio.