WARNING: Potential spoilers ahead. Expand at your own risk.
Short answer: Yes and no.
Longer answer: Before I wrote book 4, I had begun a short novella that would have taken place shortly after book 1 and involved a couple of characters from that book. I never finished it, but it's still there in my files. When I wrote book 4, one of the side characters had such a strong presence and loud voice I thought maybe I could keep the series going. I even came up with concepts, titles, and book covers for 3 additional books to add to the series. But book 4 burned me out so much I couldn't even think of going back to it, so the idea, along with all its notes and materials, got shelved.
With that said, I still love this world and the characters in it. The ideas I came up with are still intriguing enough that I want to come back to them eventually. No promises, but I am strongly considering it.