I just finished a book in a new series (The Celestial Service) and I figured a way to tie it in to the History Patrol -- win! It's an idea I had about the guardian angels in the Patrol and how I can write their stories and tie them to the Patrol.
I'm going to work on this whole concept next year, and I hope in 2020 I'll have a revamped History Patrol series, with another trilogy of books about their guardian angels.
Keep your fingers crossed -- there's a lot thinking going on!