We’ll be honest, we haven’t kept track of how many actors have been rumored to fill a potential role in the upcoming HARRY POTTER series. It has been pure speculation on whether the likes of Rachel Weitz or Cillian Murphy will get to take on iconic roles or not. The only confirmed actor locked into a role is John Lithgow. 
The prolific actor has confirmed the most recent rumors that he’ll be playing Professor Albus Dumbledore in the series. Actors like Mark Rylance and Mark Strong were also rumored for the role. Lithgow, noted for roles in works like 3rd Rock From The Sun, HBO’s PERRY MASON, and Conclave, commented to ScreenRant about his latest role. He stated,
“It came as a total surprise to me. I just got the phone call up Ron Weasley and Hermione Granger, at the Sundance Film Festival for yet another film, and it was not an easy decision because it’s going to define me for the last chapter of my life, I’m afraid. I’m very excited. Some wonderful people are turning their attention back to Harry Potter. That’s why it’s been such a hard decision. I’ll be about 87 years old at the wrap party, but I’ve said yes.”
Keep in mind, the series is said to be a close adaptation of J. K. Rowling’s novels and that each book, and subsequently each movie then, will take one season to flesh out. That will keep Mr. Lithgow busy for several years, if all goes well, as the grand wizard Dumbledore is prolific throughout.
Exactly who joins him in the series, as we’ve mentioned, at this point, is a lot of guesswork and wishful thinking. Both Rachel Weitz and Sharon Horgan have been rumored for Maggie Smith’s Mrs. McGonigall, Cillian 
Murphy for Ralph Fiennes’ Voldemort, Ben Barnes for Gary Oldman’s Sirius Black, Brett Goldstein (pictured) for Robbie Coltrane’s Rubeus Hagrid, and Paapa Essiedu for Alan Rickman’s Severus Snape. The latest seems to suggest Phoebe Waller-Bridge could have the role of hateful aunt Petunia Dursley, played in the films by Fiona Shaw. All of those roles should flesh out soon, but the key roles of Harry Potter, Ron Weasley, and Hermione Granger might take a while longer, as an open casting call has been issued for those roles.
HBO has not officially made a statement except the following:
“We appreciate that such a high-profile series will draw a lot of rumor and speculation. As we make our way through pre-production, we will only confirm details as we finalize deals.”
The series will be filmed at Warner Bros Studios Leavesden and is slated to debut on HBO in late 2026 or early 2027.
