In what could possibly the best news I've heard about the new Star Wars film both J.J Abrams and Lawrence Kasdan, writer of Empire Strikes Back, Return of the Jedi, and Raiders of the Lost Ark, are taking over the writing duties for the new film. After Michael Arndt, writer of Catching Fire and Little Miss Sunshine, was originally tapped to write the movie last November but even after different treatments it seems they're handing it off for some serious punch up. And who better to punch up your film than Kasdan and the director himself.
So maybe you look up Kasdan and think Return isn't on par with Empire, you're kind of wrong, but he did take Star Wars from a crucial beginning phase into the franchise we know today. George Lucas only had A New Hope in mind when he was originally creating the series with idea pockets for what would eventually become a much grander universe. Without Kasdan that universe wouldn't exist, neither would the dark turn you get in Empire, and those same dark tones throughout Jedi. Tapping him will not only appease Star Wars aficionados like myself but could lead to an overall better movie, hopefully.
As for Abrams his history of writing isn't weak either. LOST, Fringe, and Super 8 are some of his best and I don't think it's a bad thing to have a director's hand in the writing. Perhaps being in the writer's room will help push out a more cohesive and specific vision. Abrams is known for growing up a Star Wars fan and having a true fan craft the next film leaves its fate in good hands.