"Eldest" is not currently a film as of 2015. Rumors exist surrounding the potential for its release as a sequel to the 2006 film "Eragon" because it is the sequel to the novel "Eragon" by Christopher Paolini (on which the movie was based). If it were to become a film, it would presumably follow the plot of the novel titled "Eldest," which follows the adventures of Eragon and the dragon Saphira.
The plot of Eldest begins just after the end of the previous novel. The protagonist, Eragon, and his dragon, Saphira, travel to the realm of the Elves to continue Eragon's training as a Dragon Rider. As in the first novel, several secondary plot lines complement the protagonists and build the themes of the story, including friendship, forgiveness and responsibility.
Many of the characters from "Eragon" reappear in "Eldest," and the novel introduces some new characters as well. Eventually, Eragon and his dragon face off against a new Dragon Rider, Murtagh, and his dragon, Thorn, at the Battle of the Burning Plains.
Though rumors popped up about an "Eldest" movie following the release of "Eragon," box office sales were lower than expected, and no solid plans have emerged for the production of a sequel.