This weekend during Star Wars Celebration, a panel was held to discuss Rogue One. It is still in the movie's development cycle but Gareth Edwards (director) did drop a few tidbits of information. To start the new official title is "Star Wars Anthology: Rogue One" with Anthology added to differentiate the movies from the upcoming trilogy of films.
One of the most important bits finally provides a little insight on what the movie is about. The official synopsis "A band of resistance fighters unite for a daring mission to steal the Death Star plans in Star Wars anthology film, Rogue One.” This places the movie just before the beginning of the very first Star Wars film. The one known cast member, Felicity Jones, will play one of the rebels that steals the plans. Because of when it is set that means all the Jedi are considered extinct (except for the random few that will probably pop up as various movies, cartoons, and books need them too) so it will focus on characters without any power sets.
The last bit is the genre of the film. On the surface it sounds like a heist movie but apparently Edwards inspirations for the film are military in nature such as Black Hawk Down and Zero Dark Thirty where its a few against many and the potentially amoral decisions that must be made to survive and complete the mission. The image to the right is test concept footage that was shown during the panel.