Benzema can surely play for more years however I doubt he would be able to play like this in those years also. Because I don't remember Benzema playing this much awesome in the previous years too. Of course I don't mean that he was bad then. But this is like a career-high season for him. And I don't believe he can have a season like this anymore from now on. And when Mbappe comes, Benzema is very likely to be in the subs unless Real Madrid change their formation. Of course Mbappe will need to earn his place in the starting eleven but I don't think that it would take a very long time.
I understand where you are going to, and we need to understand that Benzema has never been a bad player. He has been an excellent player for real Madrid. Not only an excellent player, he is also a loyal player. When Ronaldo was around, he played under Ronaldo and I think this is just the season of his reward. I wouldn't know if I should say that he is lucky his prime is coming at his old age. Would it be better it came when he was younger?
Be it all, I am happy for Benzema who was once ignored for world Cup by his country. Now, he should be sought for.
Benzema still has two years to give us what we witnessed in him this season. Even if Mbappe arrives Madrid, he cannot take Benzema position. Benzema can only be benched because of age and not performance because his position I different from Mbappe's