Yes, Chadwick will be portraying Black Panther in What If…?, but it was, unfortunately, his last portrayal of the character before his death in August 2020. According to the New York Post, he recorded his lines for the show shortly before he passed away following a four-year battle with colon cancer. For now, we’re only getting one season of the series, so we don’t know if Marvel will give us a second season or how many lines Chadwick was able to record before his death.
On What If…?, this version of Black Panther is Star-Lord and works alongside Yondu. But in the MCU that fans know and love, Star-Lord is actually Peter Quill, who’s a member of the Guardians of the Galaxy. Yondu is essentially Peter’s adoptive father who taught him everything he knows.
Other changes in What If…? that aren’t in the MCU include Gamora being one of the Avengers and the Vision trying to remove the Mind Stone from his own head. Just from the trailer, we can also see that Loki is the king of Asgard, Peggy Carter is a British version of Captain America called Captain Carter, and Wanda Maximoff battles it out with General of the Dora Milaje, Okoye.
Source : https://www.distractify.com/p/is-chadwick-boseman-in-what-if