When does Wings of Fire return?

Wings of Fire is a series of high fantasy novels about dragons. The series has sold over 27 million copies and has been on the New York Times bestseller list for over 200 weeks. The main series currently consists of three arcs of five books apiece, which focus on young dragons including Clay, Glory, Starflight, Sunny, and Tsunami, fulfilling or subverting prophecies to save their world.