Square Enix seems pretty firmly behind Final Fantasy XIII protagonist Lightning. In addition to the conclusion of her saga in Lightning Returns, as well as cameos elsewhere, Lightning will be able to fight alongside you during a special Full Active Time Event in Final Fantasy XIV: A Realm Reborn.
Players will also get to dress up in Final Fantasy XIII themed costumes—Lightning for the ladies and Snow for the dudes—and wield weapons from the RPG upon completing the event.
In the spirit of fairness, a return favor is being delivered to Lightning Returns: Final Fantasy XIII, which will be getting a hidden Miqo'te costume and more from A Realm Reborn. See that along with swords and shields themed after FFXIV states Gridania, Ul'dah, and Limsa Lominsa (in that order) below.