The article I saw on Vol. 3 wasn't for a prequel, it was to tell the story of Vernita Green's little girl seeking revenge on the Bride for killing her mother.
You can read the article here:
http://jam.canoe.ca/JamMovies/apr9_kill-ap.html
edit to add that I re-read your reply and you already noted that it could be about Nikki seeking revenge. So there you go, more to go with on that theory.
