Both filmmakers have a history with George Lucas. David Fincher served as an assistant camera man on Star Wars: Episode VI - Return of the Jedi, and Jon Favreau used George Lucas' Skywalker Ranch for the sound mixing on Iron Man. Jon Favreau also guest starred in a voice role on the animated series Star Wars: The Clone Wars.
As with most stories regarding Star Wars: Episode VII, nothing has been confirmed by LucasFilm or Walt Disney Pictures. All we know for certain is that Michael Arndt is writing the screenplay,