Quick Theory: Big Mom is being cleared from the story it seems. That means her devil fruit will become available once again. Big Mom and Nami have been character foils for some time.
“Big Mom is being cleared from the story. That means her devil fruit will become available once again. Nami has evolved into a different type of motherly figure. If Nami gained the Soru Soru no Mi, it would be a handing on of the baton.”
Big Mom is toxic maternalism. While her ambition is to create and equitable and inclusive world, she does not allow free will. She creates the world she wants through manipulations. She steals soul energy to generate servants to her will. She uses her own soul to create weather weapons. She marries her kids into beneficial alliances.
Nami has evolved into a different type of motherly figure. She was very manipulative in the beginning of the story (Arlong Park.) But she learned to be trusting. She is willing to sacrifice for her Nakama (Whole Cake Island.) And she genuinely protects children (Punk Hazard.) Nami is not saintly, but she has grown significantly. The fact that Zeus defected from Big Mom says a lot about Nami’s character.
Nami inheriting the Soru Soru no Mi, would be a handing on of the baton of matriarchy (pun intended.) While BM failed in her dream, Nami could use the devil fruit and it’s creative potential in service of a more balanced version of BM’s dreams where people still possess free will. And in terms of powers, Nami would become much more of a fulfillment of her “weather witch” persona. BM in effect already showed Nami a skill: maser saber. Nami is a glass canon in need of a major power boost through either haki or devil fruit, and BM’s fruit looks like it’s available.
Lastly, in the film Red movie trailer, it appears the Sunny’s masthead has come to life? Assuming the movie is a flash forward, one fruit that could perfectly explain that is the Soru Soru. If Nami gained that fruit at some point, she could test it out on things on the ship