I do not think Ronaldo will stop playing at the end of his contract. He likes this game very well and with the way he plays, it is obvious that he still wishes that he was young. Ronaldo will not retire at 40, he would like to play for as long as his body can permit. So, what I feel is that he will have a contract renewal at the end of this one, and it may be even better because of what has been offered to other European players that have moved to Saudi Arabia's league. Al Nassr will try to beat it, to keep him happy
No one knows what will happen next when Ronaldo's contract ends at Al Nassr, whether he will extend his contract or look for another club outside of Saudi Arabia. In fact we will see that only Saudi Arabia has the ability to sign Ronaldo and at his old age it is difficult for him to return to Europe and also the salary considerations make any club outside of Saudi Arabia consider signing him. After all if you look at his playing ability, it is still clear that Ronaldo's presence in the team can have a positive effect on the club and his contribution is still quite large so far.
And I'm sure that in the end Al Nassr will extend Ronaldo's contract and it must be admitted because it was the Ronaldo effect that made many European players eventually move to Saudi Arabia. So that this business continues, in the end the club owners benefit greatly from the project they are developing and naturally Ronaldo will have his contract extended.