I like your statement "If" they beat Milan, then Hakimi would be very much qualified to be the next African footballer of the year, cause of his good contribution to his team Paris Saint-Germain in both the Champions League and French Ligue 1 moreover he's already won the Ligue 1 so winning the Champions league would make him the best candidate for the award.
Failure for his team to win the Champions league, then Mo Salah would be the favourites candidate followed by Hakimi or Osimhen, I believe they might even consider him as runner up before Osimhen due to how relevant his league is compared to the Turkish League, Osimhen has been spectacular this year if only he was playing a bigger team in one of the top leagues.
If PSG fails to win the Champions League it will reduce his chances of winning the award. A loss will put the Morrocan player in the same class as Victor Osimhen and Mohammed Salah, who both won League titles. Salah might have a slight edge considering that the English Premier League is highly rated than the Turkish and French League. But in my own view, Hakimi still stands a better chance of clinching the African Footballer of the Year since his club made it to the UCL finals.