Lupita Nyong'o does not know if she will return to the galaxy far, far away in Star Wars: Episode IX yet. Following her Oscar win for 12 Years a Slave, the actress was cast in J.J. Abrams' The Force Awakens as Maz Kanata, an old alien ally of Han Solo's who bestowed wisdom to Rey and Finn. Though the role was just a small supporting one, the character was still quite important to the plot, as she was in possession of Luke Skywalker's old lightsaber - a good question that unfortunately may never be answered in the sequel trilogy. Though the original plan for Episode VII saw Maz follow the heroes to the Resistance base, she ultimately stayed on Takodana.
Maz returned in The Last Jedi via hologram, where she set Finn and Rose on their mission to Canto Bight. She had even less to do in Episode VIII than Force Awakens, raising questions about how she could fit into the saga finale, which Abrams will direct from a script written by him and Chris Terrio. As it turns out, Nyong'o is wondering about Maz's future as well.
In an interview with THR, the actress briefly commented on a possible Star Wars return, telling the outlet, "I don't know yet. I'll know soon." Per reports, the plan is for Episode IX to begin production this June, meaning casting decisions will have to be ironed out in the near future. Lucasfilm likely won't make any official announcements on that matter until the cameras start rolling, much like they did for Last Jedi. Abrams pitched his story to Disney last month, so the higher-ups probably have some idea.
Since even those who loved The Last Jedi will admit Maz's inclusion in Rian Johnson's film was a bit awkward and forced, an argument can be made that she has no real function to serve in the narrative anymore. However, Last Jedi specifically mentioned the Resistance has allies in the Outer Rim, and news of Luke Skywalker's heroic sacrifice spread across the galaxy to inspire others to join the cause. Perhaps when Episode IX picks up, Maz will be an official member of the Rebellion, aiding them in the fight against the First Order. In Force Awakens, she didn't seem like she was one to back down, so it stands reason to believe she'll answer Leia's call. And even with Poe Dameron learning valuable lessons in leadership, the Resistance could use some more powerful voices at the top.
At the same token, it's not like Episode IX is going to hinge on whether or not Nyong'o comes back to the fold. Though the character has her fans, she's hardly an integral part of the sequel trilogy ensemble and there are more than enough meaty storylines for Abrams to explore without having Maz there too. Some might argue she deserves some form of resolution, but she's more or less an afterthought (given all that happened in The Last Jedi) with little more to contribute. Though, Abrams was the one who made her a part of Star Wars lore, so he'll probably try to find a place for her as the trilogy closes.