The film’s writer and director has begun storyboards for the films and intends to ensure that each of the three films tie together into one true story, hoping to avoid feeling as though each film is a different story with the same character’s thrown in:
“There are certain characters and situations that come into play in the second film that will becomes much more crucial to the story by the third. Other threads from the first will begin to pay themselves off in the second,” DeBlois said. “It’s my way of guaranteeing that it is not another adventure that we throw the same five or six characters into, that it feels like part of a larger story.”
THR also reported on the second film’s plot:
The story will move beyond the small, North Sea island that was the setting of the original film as it traces the further adventures of Hiccup as he grows toward becoming the leader of his Viking clan.
The first film was wildly successful both critically and in the box office, so it comes as no surprise that the film’s creators are looking to continue the story.