I second DeKalb Daddy . And also, remember that just because this specific plot closes, it doesn't mean that you won't have more opportunities in the future with the minor characters or completely unknown characters.

I know C.J. Cherryh had one series that the first book set up and the second book happened a generation later. I'm sure she's not the only one. Allow yourself to be open to continuing in this world without it specifically being these characters, and you might find more openings once the novel is completed.