When does Tome of the Unknown return?

"Tome of the Unknown: Harvest Melody" is a 2013 animated short film created by Patrick McHale and produced by Cartoon Network Studios. In the film, Wirt (Elijah Wood), his brother Gregory (Collin Dean), and Beatrice (Natasha Leggero), a bluebird, head to the big city in search of an arcane book of all known things. The film serves as the inspiration and pilot for the miniseries Over the Garden Wall.