They'll bring her back... during the last 2 minutes of the game like XIII. They said Lightning gets a happy ending, and Serah being alive depends on that. But she won't come back any sooner than the very end. They can't resist adding in two trillion tons of melodrama and angst.
:T Good point..
"In the hands of someone who's good enough at thinking outside of the box, ANYTHING can be used as a weapon."