The offer Real Madrid received for Vinicius Junior from Saudi Pro League clubs is tempting, and if Real Madrid decides to let Vinicius Junior move to the Saudi Pro League, the money they will realize from the Vinicius deal will help them sign a lot of players from different clubs, but I think Real Madrid isn't yet ready to sell Vinicius Junior, and Vinicius Junior won't want to move to the Saudi Pro League because he still wants to play for Real Madrid and have a chance of winning personal awards like the Ballon d'Or Award, so any possible deal for Vinicius Junior to move to the Saudi Pro League won't happen this season.
Vincius is an incredible player, smart, clinical, and decisive. Real Madrid wont want to lose a precious gem at his stage they are trying to rebuild the team to what it was in the past. We saw how they lost the La Liga to Barcelona, lost 4 matches against Barcelona and also were eliminated in the Club World Cup by PSG. That alone is enough reason why Xavi Alonso can never let Vinicius go, so far he is one of the remarkable and experienced player in the squad, so until the squad sits well with him, Vinicius still remains.
You are right that Vinicius Junior is a morale booster for Real Madrid and he is a talented player who makes decisions. We have observed that at one time, this player was the mainstay of Real Madrid Football Club's attack, meaning he was the most prioritized player there. So it is not right to consider that he might be released by this club very soon, perhaps his impact is currently diminishing a bit, but even then, perhaps his contribution here is much greater than Mbappe's. If Real Madrid Football Club wants to win the El Clasico matches with Barcelona in the upcoming season, I think they must give the Brazilian player the highest priority there.