I agree completely with Mirage that it wouldn't really add anything to the game to show Lightning have a love interest. Love is a far too cliche and exaggerated theme in storytelling. The last thing we need is another shallow, automatic, unbelievable romance like Tidus/Yuna that just flies out of nowhere as if to say "none of the writers at Square have ever experienced actual love, and this is how we think it goes... underwater... with bubbles... and crystals... and smiles... and an awkwardly voiced asian girl who sounds like a cat singing atmospherically all around you"

I appreciated that 13 did not have a love story ingrained in it, unless you count Vanille and Fang's tastefully understated relationship. They were the most realistic couple in the entire FF series (I don't care if you don't think they were a couple, personally, but it seemed pretty clear to me in the way they treated one another and reacted to each other). I think the romances of most FF games have been stereotypical and predictable. I really don't think the series needs more unless they want to explore some new themes. For example, I think it would be nice to see a male-male romance in one of these games at some point. That would be interesting and not cliche, and as colorful as FF male characters usually are, it could be pretty spellbinding and dramatic. Not to mention damn near every gay dude I've met loves Final Fantasy, so I think it's about time Squenix threw them a bone for all their contributions to the fandom, but that's a whole different topic.

In short, no love for Lightning. It would soil her awesome character. She's too much of a lone wolf and too driven by her whims and convictions to really settle down anyway. She'd just be running off to fight all the time like that noncommittal d-bag, Snow.