"Star Trek and Star Wars have some major built-in sectarian differences, which aren't immediately apparent to outsiders. One is science fiction, the other science fantasy. One is resolutely humanist, the other revolves around a mystical religion. One is set centuries into Earth's future, the other who-know-how-long ago in the past of a whole other galaxy. One began on TV and got canceled after 3 seasons, forcing its creator to beg for financing; the other hit the big screen like an atom bomb, and when its creator attempted to abandon it after 3 movies, the fans wouldn't hear of it."
Behind the scenes, however, the two franchises have been inspiring each other, and sharing personnel, for years. J.J. Abrams will hardly be the first player to switch sides.