I assume they keep her around as a yearly event due to the Japanese always respecting who/what came before. It's also an easy way to make FFXI vets who do come and play FFXIV eventually feel like they are seen. She's also a curiosity drive, particularly towards those who are vulnerable to wanting every scrap of content with their waifu in it. Makes'em go try XI out, and let it get a little more profit so they can excuse the little toasters they have it running on still.

It would be cool for her to be a character in XIV, but it'd also just be a little weird. Her entire schtick in XI is to be a time traveling daughter of Tenzen who served the player character in the dark future where the Cloud of Darkness began to erase Vana'diel (in this world, Cloud of Darkness is an extraterrestrial entity more powerful than the Goddess Altana). The entirety of her scenes in XI are her showing up, laying out your great destiny. Occasionally fighting something, and then suffering time traveling paradox phase out/erasure, only to be brought back by being imbued with the Phoenix from Tenzen's blade. She does fight Cloud of Darkness with the player at the end of Rhapsodies of Vana'diel, but after that she's pretty much not present within the game (though I haven't been back to do Voracious Resurgence yet).

With that in mind, I have no idea how they'd shape her in XIV, since she's more of a plot device than a character.