While in game, her story line hasn't moved forward since vanilla, I believe her background lore has been set up quite well. As the theory goes, the stranger was one of the researchers in the ishtar collective that got trapped in a vex mind. Once they escaped, they began exploring the vex network and have thought to be stopping calamity by influencing what were once established events. Why, just look at how her influence shaped our fledgling story. Tl;dr: If she happens to not show up in game, she'll probably get some vague links in the grimoire. I'm personally interested to see if she'll show. Both possibilities provide interesting paths for the lore