There is still speculation about why Roberto Orci left Star Trek 3.
Rumor mill has it that it was for one of two reasons.
The first story is that Orci quit because “Paramount’s notes on his script were untenable.”
Another story claims that Paramount “shut the picture down a month ago and spent the time talking to other filmmakers before officially taking Orci off the project,” with Edgar Wright being offered the director’s chair.
Paramount would like Star Trek 3 to be “huge,” said Badass Digest, and more like Guardians of the Galaxy.
Source: Badass Digest