HBO's head of IP, Sarah Aubrey, briefly talks about casting

When asked if actors approach her for roles, and if any of the original actors will be back;

Yeah, I think it’s a dream job for a lot of actors in the U.K. But the roles that we’re casting right now are for people who are going to be on the show for a decade, so that’s also a very particular gig. But the commitment is to make the books, and that’s what it could be. But there are interesting people raising their hands to be the featured adult actors that come on in later seasons, like the Sirius Blacks of the world. So, it’s been very, very fun, but we don’t want to repeat people that were in the movies. And it’s always a little nerve-wracking because people so associate those roles with certain actors, but I also think because it’s going to be eight hours of TV, we’re going to immerse them in a different actor’s performance.