I believe next season will be different and we might see a lot of transfers especially in the Al-Nassr squad to improve the team, especially the defence line where we can see easily the difference between it and Al-Hilal. The number of received goals is almost twice as higher in the Al-Nassr side.
Cristiano Ronaldo hope were big in the beginning of the season and the team was lucky to find the second place again and finish behind Al-Hilal.
Even if Al Nassr needs to build their defense, I think they don't need to buy many defenders. 3 defenders is enough to strengthen their defense line. Aymeric Laporte and Alex Telles have performed quite well, they only need 1 centre-back and 1 right-back. 1 defender may be for the substitution if there is a defender who can't play well. Another line should be improve is midfield line, they need 1-2 central midfielder. For the attacking line, I think Al Nassr has enough player (Ronaldo, Talisca, Mane). If they want a new attacker, 1 attacker is enough. But I really expect that Al Nassr will buy younger players this time. They already have too many old players in their squad. It really bring influence for the team.
The new coach is also important. I'm not sure if they can play better of they only keep the current coach. The current coach can't make Al Nassr stronger, the new coach is needed for the next season.