Book 6: Nightfall

When Lodestar was released, Shannon Messenger announced that there would be a book 6 and 7. She also said that Book 6 would be released in Fall 2017. The title has been chosen, Nightfall, and was released on 1/31/17. Shannon also said she hasn't yet decided on anything else about the story. However, on her blog, there was the quote "The star only rises at Nightfall."

Title released here.