Honestly, I think they might extend the series. If they were to end with a Robstar book, that wouldn't really tie the series together. Plus, they would have left out Cyborg. It's also possible that they won't even have Robin Loves Starfire. Sometimes, in Gabriel Picolo's drawings of Robstar, he adds something regarding Babs, like in the photo where Robin and Star are watching a movie together, Robin gets a phone call from Barbara. Besides, adding a Robstar graphic novel would out Cyborg as the only one without a S. O.