If there is a Volume 3, here's what I think should happen.
*First of all, I think "Kill Bill" should still be in the title because I doubt that Bill is actually dead. I don't think that Bill would be stupid enough to tell anyone about a fighting technique as deadly as that "Exploding Heart" thing and, what's more, sending at least two of his proteges (Beatrix and Elle) to the martial arts master that taught it if there was a possibility that it would be used against him. The "Exploding Heart" thing was a hoax, pure and simple. It was just a very convenient ruse that Bill used to deceive Beatrix into thinking that she had killed him. Bill probably just laid still in his back yard for a few hours until he was sure that Beatrix and B.B. had left. Also, if the exploding heart thing had been real, Elle wouldn't have been able to kill Pai Mei, because Pai Mei would have used it against Elle in self defense. So seeing as Bill is still alive, he'll probably round up a new assassin squad, perhaps using superhero names as aliases. Which makes sense as Bill loves comic book superheroes.
*Elle, of course, is almost certainly still alive. She'll probably take on the name Daredevil as she, like her comics namesake, is blind and could easily be the "woman without fear." And like Daredevil, her hearing will become super keen so she can track her enemy's every move, just by listening. She'll use Budd's Hattori Hanzo sword.
*Sophie Fatale would return as the new leader of the former Crazy 88's. She'd be known as Cyberiad as she'd have a new pair of robotic arms with super fast reflexes to replace her original ones. The Crazy 88's would be redubbed the Cyber Squad as most of the survivors will have robotic prostheses after encountering Beatrix the first time. She'll use O-Ren Ishii's sword, which I'll bet was a Hattori Hanzo.
*Of course, little Nikki (Vernita Green's daughter) will be on Bill's team, too, once we've given her 10 years or so to mature. Nikki will, of course, be the Punisher as she will be out to avenge the death of her "family," just like Nick Castle. Nikki probably wouldn't fight Beatrix but instead would come up against B.B. who would be defending her mother. For this duel, Bill would lend Nikki his Hattori Hanzo, and Beatrix would have to lend B.B. her H.H.
*Bill will dub himself Superman, of course, and we'd finally have a decent battle between him and Beatrix.