Sadly, that was indeed the end of this story. I'm on board with all of you though; when I got to the end, I was just as disappointed by it. I thought there was going to be more too. It left a lot of questions unanswered and was a bit anti-climatic (in my opinion), but that was most likely Mockingbird Julia's intention. Perhaps she wanted to write a sequel detailing what happens to the slaves and Serena's father's reaction to her marriage to Darien, though never wrote it. However, since I am not the original author of this story, I do not feel that I have the right to author its sequel.
So it's up to your imagination of what happens to them because that is not a story I cannot tell.
Wishing there was a sequel too,