I think Saudi Arabia will qualify for World Cup using any possible way.
They spent a lot of money to buy Ronaldo and other European players, they also become the sponsor for Club World Cup, after everything they done for football, would they accept if they're not qualified for World Cup.
Ronaldo hired by Al Nassr because they want Ronaldo can help them to broke the domination of Al-Ittihad on Saudi Pro League and gets the trophies on that competition so in my opinion there is no related between him with Saudi Arabia chances to the world cup
Speaking about Saudi Arabia currently they will fight at 4th round and they only have 2 games remaining before reach to that competition assuming they can won from Irak and Indonesia automatically Saudi Arabia will went to the world cup and Saudi Arabia has good chances to do that especially they playing as a host on that round