Because it's being written and directed by Rian Johnson.
You might be saying "Who's he?", he's the guy that directed from what I've been told the best Breaking Bad episode Ozymandias, and he wrote and directed one of my favorite films along with Eternal Sunshine of the Spotless Mind, Brick. [S]he also wrote and directed looper but let's excuse that[/S]
I don't think I've been this hyped for a film ever.
http://www.starwars.com/news/rogue-one-is-the-first-star-wars-stand-alone-film-rian-johnson-to-write-and-direct-star-wars-episode-viii