This might be considered more by Robert Lewandowski when his contract with Barcelona is over even though there are many other things that are still very open to happen to him in the future. Because as you said that at this time Robert Lewandowski is still very much needed by the Barcelona team because he can still help more young players to develop in the Barcelona team. And the choice to go to the Saudi Arabian League is actually very good for him before he really hangs up his boots from the world of football.
Robert Lewandowski can give his best for Barcelona before his contract ends and now his job is to focus on finishing the season with some much better achievements. Barcelona will not let go of Robert Lewandowski before his contract ends because his contribution is still needed enough to help the team achieve something that is expected and his presence can also provide a better front line. Regarding the future after his contract ends, it can be considered later, whether he plays in the Saudi Arabian League or not before entering retirement in football.
Lewandowski's contract ends in the 2026 season and I think before that Barcelona can sell him to a Saudi Arabian club so that Barcelona can make a profit because if he waits for his contract to end he will become a free agent and Saudi Arabian clubs will compete for this player, yes even though Lewandowski is an important player for Barcelona but at the age of 37 Barcelona certainly needs new regeneration and the sale of Lewandowski can be used by Barcelona to recruit younger players.
You are making some interesting plans for Lewandowski, but it's strange that you know so much about Lewandowski's plans and preferences for his last path in his career. Lewandowski going to Saudi Arabia doesn't sound convincing as he is not the same person as Ronaldo. He would not be willing to get sold against his own plans for his future only because Barcelona can make some profit then. He is extremely fit physically and I think he might return to the Bundesliga or give it another year or two in a European top club accepting a role as a substitution player, a joker for the later game or maybe sometimes as a starter because he is still easily able to compete with the best strikers in the world.
He is not prone to injuries, he is leading the La Liga top scorer list ahead of Mbappe and Raphinha, he is scoring around one goal per 91 minutes. This is not the time for him to contemplate a 180° change in his career or even going to Saudi Arabia.