Celes (C'mon, Anything's possible)*Votes*
But seriously, I feel that, had he lived, she most likely would have been with Leo. The dialog between the two aboard the ship seemed to hint at some future feelings. Sadly, his untimely death crush any possibility.
Shadow and Terra seems to be a reasonable conclusion as well. He seems to open up to her on the boat more so then he has to anyone since Baram died. Still, he too suffers Leo's fate, so it really isn't a possibility any longer.
Terra and Edgar? Why? Yeah, sure, he says a couple of things to her early in the game, but that's just because he's a womanizer. There is really nothing to suggest as the game goes on that they have any feelings for one another.