Please say Leona will have her lore expanded at some point
My theory on how things could go:
After being trained by the Solari, Leona is sent on a pilgrimage as a way to give her some worldly experience. When Diana awakens and murders the Elders, though, Leona returns upon sensing something amiss, and finds the chaos Diana has created (with Diana herself long gone). Leona goes back out to find Diana, hoping to bring her back peacefully.
Said search will have Leona cross paths with certain other Champions (hint
hint), and learn a few... unsettling things about the Solari order that the Elders didn't tell her.
:Down with the sun. The night shall rule.