It is kinda confirmed through an e-mail I recieved from Claudia Gray. Apart from the Balthazar book coming out পরবর্তি about guess who? Balthazar, as the name suggests. But there is a new trilogy she is currently working on called "Spellcaster". The first book "Spellcaster:The Fire". It's about witchcarft,demons, and Mexican food. Yes, Mexican food.

Straight ffrom e-mail: "Right now I am working on the first book in the upcoming SPELLCASTER trilogy, which is tentatively titled SPELLCASTER: THE FIRE. (That could definitely change, though!) It's about witchcraft, and demons, and Mexican food. আরো details about the story will come as I get further into the book!"

Sincerly,
SnowyMoon