Quote Originally Posted by Werecanary
Sephiroth is on almost every promotional footage so one way or the other I believe he'll be in the movie.
Aeris will probably be a flashback or something like that.
(SPOILER)It's already established by previews that Aerith will appear in both a flashback and in a dream-like sequence in Cloud's mind where she tells him to forgive himself for her death, and that Sephiroth's form will appear in the film during the present. The nature of his form's appearance has yet to be disclosed.