So far there has been no continuation of negotiations between all parties, so it is not certain that Dybala will join Al Qadsiah. However, it is very likely that in the end Dybala will join Al Qadsiah, especially if he is given a very attractive offer. As you said, Dybala's transfer will benefit all parties. Speaking of Al Qadsiah, Qadsiah has actually brought in several newcomers from outside Saudi. However, some of the newcomers they brought in do not have as big names as the three players mentioned in this post.
With recent activities and finished transfers of AS Roma on transfer market this summer, they can need to sell Dybala to balance their finance but they can not sell him if their plan is ambitious and want to keep Dybala one more season to achieve higher position in Serie A and want to win Europa League title in this season.
They have reasons to sell Dybala and also have reasons to keep this important attacking player for their club. The transfer market will close in less than two more weeks and we will know future of Dybala in Roma soon. Al-Qadsiah need to buy a big star player like Al-Nassr wanted Cristiano Ronaldo, Al-Hilal wanted Neymar and Al-Ittihad wanted Benzema last summer transfer.
Well, there is no doubt that that is the reason he is called the GOAT. Because he is the best player, even at almost 40 years old, he can still adapt to the young players at Al-Nassr. I think it's very rare to come across a player at this age who is still playing as well as he is.
He considers himself as a GOAT but not all people think he is a GOAT. Messi fans don't see him like such and neutral fans have people who don't consider him as a GOAT.
His ambition helps him to grow up his career since his time in Sporting Lisbon and Manchester United, became one of biggest star players in last twenty years and now at his age nearly 40, he is still able to play, run well and score many goals. It's impressive and he does not need to be recognized universally as a GOAT.