Rumors suggest he will appear on the Netflix drama alongside Salim Dau, who will take on the role of Dodi's father, Harrods boss Mohamed Al Fayed.
Film producer Dodi was killed alongside Diana in a 1997 car crash in Paris, France.
About her casting, the 31-year-old previously stated, "Princess Diana's spirit, her words and her actions live in the hearts of so many. It is my true privilege and honor to be joining this masterful series, which has had me absolutely hooked from episode one."
Meanwhile, Imelda Staunton will replace Olivia Colman as Queen Elizabeth II and other newcomers include Claudia Harrison, Theo Fraser Steele, James Murray, Dominic West, Lesley Manville, and Jonathan Pryce, who will portray the late Prince Philip.
"The Crown" is coming off a big win at the Emmys on Sunday night, September 19, when the show claimed seven top prizes including Outstanding Drama Series and victories for writer/creator Peter Morgan and castmates Olivia Colman, Josh O'Connor, Gillian Anderson, and Tobias Menzies.
Winning his first-ever Emmy, O'Connor said during his speech, "Thank you so much. That's the first line [of my speech]. Making the crowd has been the most rewarding two years of my life, and the cast and crew, Peter Morgan, our producers and all the brilliant directors who made the show such a pleasure to be a part of, thank you."
The 31-year-old actor, who played as young Prince Charles in the hit Netflix series, additionally thanked co-star Emma Corrin, who starred opposite him as Princess Diana. "Emma Corrin, you're a force of nature. I love you very much," he gushed.