When does Wings of Fire return?

Wings of Fire is a series of high fantasy novels about dragons. The series has been translated into over ten languages, has sold over 67 million copies, has been on the New York Times bestseller list for over 200 weeks. The main series currently consists of three arcs (soon to be four) of five books apiece, which focus on young dragons. Each book centers on its own protagonist, whose story is told through a third person limited perspective.