Just standard theories to tell you the truth.

"The opening lines in the movie are spoken by a little girl, and they are something like: "Once upon a time, there was a warrior who defeated the evil known as Sephiroth. His name was...Cloud Strife." " - this isn't true... I've seen the real translation from a few sources and that wasn't it

Nice image of Vincent. You can even just about see his face!

There's been another trailer recently with screenshots on www.adventchildren.net that further prove his identity too.