The Hollywood Reporter claims that "Abrams has not committed to that release date, meaning the date could be changed if the development process requires it." This would not be the first time that Abrams has delayed a project to work on another; Star Trek Into Darkness was put back a whole year so he could get a cut of Super 8 he was happy with.
To further fuel this rumour Paramount Vice Chairman Rob Moore told LA News that "J.J. will continue to develop projects for us including a new Mission: Impossible and he is committed to produce another Star Trek." It's likely that he'll only act as a producer on both films, but if he was to jump on to Star Wars: Episode VII straight away, Paramount could be waiting a long time for their movies.
On top of all that, he's also reportedly working on a new TV show with Children of Men director Alfonso Cuaron called Believe which is about a girl with psychic powers.
Just how many hours are there in J.J Abrams' day?