At the Armagddeon Expo in New Zealand McCoy told fans he has been cast as Radagast the Brown although no contracts have been signed and filming is currently on hold due to a disupite with the New Zealand branch of Actors Equity.
McCoy had been linked with the film for some time. It is understood he’s met both Peter Jackson and co-writer Philippa Boywens.
He may have been hoping for a bigger role. In fact, Radagast the Brown (unless my memory fails me) isn’t even mentioned in The Hobbit. The character is in the Lord of the Rings but was cut from the movie.
The Istari were sent to Middle-Earth by the Valinor to help battle against Sauron.
Radagast the Brown has a connection to animals. In fact, it was Radagast who asked Gwaihir the Eagle to fly to Orthanc with news of Sauron’s troops. When the eagle spotted Gandalf was trapped on the roof he helped the wizard escape instead.
The fate of Radagast is not known. When the Council of Elrond decided to rally its forces and meet Sauron together Radagast had vanished from his house and could not be found.