According to Brickset (via AV Club), the voices we'll hear are Jackie Chan as Master Wu, Dave Franco as Lloyd, Michael Peña as Kai, Abbi Jacobson as Nya, Kumail Nanjiani as Jay, Zach Woods as Zane, and Fred Armisen as Cole. The Ninjago: Masters of Spinjitsu toyline has been adapted into a Cartoon Network animated series, a theme park attraction, as well as a video game, making it one of Lego's most popular brands. Imagine a more mystical version of the Power Rangers and that's kind of what you can expect. Here's the movie's plot according to Movie Insider...
Ninjago is the story of six young ninja tasked with defending their island home, called Ninjago. By night, they’re gifted warriors, using their skills and awesome fleet of vehicles to fight villains and monsters. By day, they’re ordinary teens struggling against their greatest enemy: high school.
Phil Lord and Chris Miller are on board to produce while Charlie Bean (Tron: Uprising) is at the helm. Maybe this will help get some buzz going for The Lego Ninjago Movie, which opens on September 22nd 2017.