Is the Kane chronicles series over?

Maybe, because on page 401 in the third book, Sadie says, "We're not done with trouble, either. I'm still worried about that murderous ghost Setne, who's on the loose in the world with his devious mind, horrible fashion sense, and the Book of Thoth. I'm also puzzling over my mother's comments about rival magic and other gods. No idea what that means, but it doesn't sound good." If there's book 4, maybe he'll write about troubles that Sadie and Carter have to deal with with Setne, and about rival magic and other gods...

I think Rick Riordan said book 3 will probably be the last book (recording) cuz he wanted to make all the fans of Kane Chronicles feel excited.

It's quite possible Rick Riordan will start a new series for Carter and Sadie, because I know the Kane Chronicles series is a trilogy, meaning it has 3 books. Percy Jackson is brought into another series, the Heroes of Olympus, from his original Percy Jackson and the Olympians series.