Aldis certainly looks the part, but I don't think they're going to cast someone in their 30s. My guess is an actor who can play late teens and early 20s. T'Challa's son was always in the mix and not a knee-jerk reaction to Chadwick's passing. I suspect the original plan was to eventually age him up for a Young Avenger's project. They've already introduced Wanda and Vision's kids, Ironheart, Hawkeye, Cassie Lang (Stature), Ms. Marvel, America Chavez, Hulk's son, and Thor's daughter. Even Heimdall has a kid.
I could be wrong, but I don't think they're time-jumping 20-30 years into the future so we can have a fully-grown, seasoned T'Challa junior with Okoye, M'baku, and Nakia as senior citizens. And relying too much on magic, the multiverse, and time travel cheapens the stakes in your story.
I'm expecting a smaller time jump, around ten years. You're not asking a young actor to be Chadwick or T'Challa. Draw from their experiences but do your own thing. He's not going to be perfect. He's going to make mistakes. We get to watch him grow into a man. If handled correctly, he could be one of the most compelling characters in the MCU, especially for young Black males.
But most folks just want T'Challa 2.0, so I'm probably in the minority with this take.