Even the best Arab players will want an opportunity to play in Europe. Nothing has really changes in the Saudi league.
I respect what they are trying to build and I hope they build a league that will captivate the whole world but for now I don't think there have been a significant change. Bringing in stars that are at the eclipse of their career isn't a new thing. America does it, Japan does it, China did it. In fact, China succeeded in persuading some young players like Oscar, Bakambu, Carrasco to join them in their league.
Building a league that can rival Europe wont take a couple of years, it will take time. And it has to be more than just the Saudi league, it has to be the whole Asian football. The can have at least 10 leagues that are very competitive just like Europe has its own top 5 leagues.
Maybe the Arab league is popular since Ronaldo joined there. before that no one even discussed it here. Ronaldo popularity can raise the Saudi Arabian League, it is increasingly known throughout the world, even Ronaldo arrival makes the Saudi Arabian League even more interesting to watch. Apart from that, what has already been said, I totally agree that the Arab League will not be able to make big changes to compete with the European League, even though they have enough money to build their league.
On the other hand European players joining the Saudi Arabian league seem to be at the end of their career and I'm not sure the Saudi Arabian League will really be famous when they don't have Ronaldo anymore. Well all these things of course are build and build and for now they are the best asian tier and it's better than before.