Who do you want writing the script for Star Wars: Episode VII? The guy who wrote a script about talking a bunch of talking toys, or the guy who wrote the the script for the best Star Wars movie of them all?
Well, if for some reason you answered "the guy who wrote the movie about toys," I've got some bad news for you. That guy is Michael Arndt. He wrote the script for Toy Story 3 and was working on the script for the new Star Wars picture. However, now Arndt is free to pursue other projects, because he's been replaced by the film's director, J.J. Abrams, and that other guy, Lawrence Kasdan.
According to LucasFilm president Kathleen Kennedy, "Arndt has done a terrific job bringing us to this point." But apparently she didn't think the job he did was quite terrific enough. So now they're going with the guy who wrote the words, "No, I am your father!"
"There are very few people," Kennedy said, "who fundamentally understand the way a Star Wars story works like Larry, and it is nothing short of incredible to have him even more deeply involved in its return to the big screen."
So Star Wars geeks rejoice...but not too much. Keep in mind that Kasdan also wrote Return of the Jedi, and is therefore responsible for the Ewoks. Plus, his last movie was a stinker called Darling Companion about a middle aged couple who learn the true meaning of love from a dog.