If there's any way to extend a successful franchise, it's taking the offspring of the prior classic characters and telling next generation stories to faithful fans. Most of the time, it never works in the case of classic stories, even though it never goes away as a genre for the sake of drawing in fans with intrigue. If you can't see the same allusions to Edward Cullen and Bella Swan's daughter, Renesmee, in "The Twilight Saga: Breaking Dawn Part 2", then you're giving "Twilight Saga" author Stephenie Meyer too much credit for not wanting to cash in.
This time, though, there may be another method in giving excuse to a new generation in the "Twilight" series. Renesmee happens to be the little-explored concept of the Dhampir, or the human-vampire hybrid. Coming from Balkan folklore, the legend is that real children were once born as a cross of vampire and human parentage. It's a subject that's seldom been explored in a vampire movie when it's perfect fodder for the never-ending teen angst horror movie.
The only other films that touched on the dhampir concept were three "Blade" adaptations starring Wesley Snipes. But that was about a full-fledged adult and not a teen capable of staying 17 years old forever. It's also prime ready for parodies in the vein of "Tabitha", the 1970s offshoot sitcom from "Bewitched" that showed another hybrid offspring of human and witch.
It's the type of genre the 1950s missed out on during the era of James Dean and all that followed about disaffected youth. Now a film can show the conflict of being both a vampire and a human without it being the result of something the teen can't comprehend or clear manic depression. This also has a chance to make the "Twilight" franchise infinitely more interesting than the Bella-Edward story, particularly because new actors could be had that know how to emote.
If it is ever done, it'll be up to Stephenie Meyer to write books on the continuing story of Renesmee. And why wouldn't she when the teen demand for "Twilight" never seems to find satisfaction in a conclusion? By the time of any movies made, young Mackenzie Foy (now playing Renesmee) would be an adult and perhaps a bigger star than the combination of KStew.
Or someone else could end up beating out the "Twilight" series to the dhampir legend. In fact, we can't be sure the dhampir legend would be made correct in the "Twilight" series considering even the vampires were given dramatic revisionist treatment from the original folklore. Yet because Edward Cullen was also theoretically a dhampir, the books and films arguably had accuracy within reach.
If dhampirs ultimately have a film legacy in vampire films, then it should go back to the Balkan tales of old to get the story completely right. One of those legends is that the dhampir isn't an attractive sort, as in possessing abnormally enlarged facial features. This alone may have to banish it from the "Twilight" universe where attractive people are what gravitates fans to those movies in a way that made them more successful than they ever had the right to be.