It has been said that the next 300 would be set before the events of the battle of Thermopylae. This rumor has officially been proven false because Frank Miller has recently stated, “I’ve written a story that’s not a prequel. It’s definitely a further story in the Greco-Persian Wars, and it involves some of the same characters but I’m not sure exactly how far along it’ll get.”
-splashpage.mtv.com
This means that bold king Leonidas will most likely not make an appearance in the film. We can count on the return of Queen Gorgo, Xerxes, and Dillios. The sequel will most likely begin where 300 left off. It will depict the battle of Platae as lead by Dillios. Although as of now the rest of the story is a mystery. The film could include any battle or event that had taken place during the Greco-Persian Wars.
Frank Miller will make a new comic book series before they start production of the film. This way the fans will be able to know if the sequel will live up to the original or suck terribly before the movie even starts production. Zach Snyder has said that he will return to direct if Miller is on board.
This information leaves me with two questions, "Will this make the story better or worse?" and "Is Frank Miller starting to sell out some of his best works in comics in order to make more money in the movie industry?"