Not necessarily. We should see Eustace Scrubb as a main character, along with Aslan. But Silver Chair, the novel, does not include his Pevensie cousins, Lucy, Edmund, Susan and Peter. Other returning characters who may or may not be included are Trumpkin (PC), King Caspian (PC, VDT), Ramandu's Daughter (VDT), and Lord Drinian (VDT).