JJ und Kasdan haben das Schreiben des Drehbuchs übernommen um im angepeilten Zeitrahmen bleiben zu können:

“It became clear that given the time frame and given the process and the way the thing was going that working with Larry in this way was going to get us where we need to be and when we needed to be,” said the Episode VII director Thursday. “Working with Larry Kasdan, especially on a Star Wars movie is kind of unbeatable,” Abrams told Deadline.
Quelle: J.J. Abrams Says "Time Frame" Of Getting New 'Star Wars' Movie Made Was Why He & Lawrence Kasdan Took Over Script - Deadline.com

Am 18.12.2015 soll es soweit sein: http://www.comingsoon.net/news/movienews.php?id=111140

So viel zu Sommer 2015.