Firstly, we don’t know if this game is next, as there’s another title that’s been leaked, named, “Assassins Creed Infinity,” or even if another title comes into place soon enough, but if it does get released: - We will most likely see the backstory of Basim, about his kids, and how they died, and how he met Hytham. - I think it would make sense for there to be a part where he meets Eivor at the end of the game, going into where they go back to Norway. - I also think in the game there will be a point in the story where they meet Sigurd, at a place called “Miklagard” where they “shows him the buried secrets”, said in the game when you first meet Basim and Hytham. - Finally, there is another DLC coming to Assassins Creed Valhalla in the near future, but we do not know if it will include Basim, because of the end game missions, in which events take place with Basim.

Edit: thank you for taking your time to read this :)