Neymar was always going to go once this took off. The man is everything i hate about modern footballers - gifted as a footballer with an attitude more interested being a celeb and wanting as much money as possible. Has no desire to work hard and be the best that the younger Neymar claimed he would be.
The threat with the Saudi's its pretty clear. They have targetted maybe 90% of players who are at the back end of their career, still decent but certainly within 2-4 years of finishing off but still no doubt better than the majority of the Saudi league. They have added some players in their prime who right now will be accused of throwing their career/talent for money, similar to those that went to China a few years ago.
The difference here is, this long established superstars that are heading over.
The next step will be for Saudi to start and compete with the European Giants for players in their prime and that is when it becomes a real problem. We are already going to be able to watch games via DAZN so interest will be their and followers will grow. You have a new generation of casual football fans who follow players rather than clubs which will feed into this, its like Fifa coming to life. The final risk will be when we see a reinvention of the Champions League to allow Saudi clubs into it to stop another breakaway led by the Saudi's and the big clubs wanting to jump ship.
I dont think this will go away like Russia did and China did.