No top strikers want to spend time on the bench, unless they get injured. As long as Benzema is in a good condition, he surely will be the main option as a CF. Sure, it may be one of the reasons why some strikers don't want to join Real Madrid soon. However, everyone knows that Benzema can play in several positions, which means he can play together with a new striker.
Benzema is still a best striker in Real Madrid with great skills and most experience. If he is healthy and ready for matches, Carlo Ancelotti will send him in. It is not depended on Benzema himself but Real Madrid and the coach actually need to have Benzema for their attacking.
It is definitely true that Real Madrid must prepare for Benzema retirement or just his less contribution because of ageing. Anyway, Benzema is still usable for Real Madrid in near future and with his attitude, I don't think he will have issues if in future, he will have a new position, as one of substitutions for Real Madrid.
When you are talking about a player like Mbappe, all teams in the world would be willing to listen to him and give him a chance to join. Real might be disappointed with him, and wanted him and couldn't get him so they could be looking for other players right now, but if Mbappe (well his agent) ever comes knocking the door, they will hear them out and if they can afford to get him (which is hard now) that means we are going to end up seeing him playing for Real, it's all about finances.
PSG kept him because they were willing to offer him insane amount, but if Real got an offer that is realistic then they would love to get him for sure.
If Mbappe is willing to accept Real Madrid's offer then it is no longer about money that is the main factor, but because of an achievement from the team's great achievements because at Real Madrid at least Mbappe has a better chance of winning many titles. Previously, Mbappe chose PSG and rejected Real Madrid's offer, obviously because of the big money he got, but as time goes on, at least Mbappe wants to achieve a lot, so Mbappe can't stay at PSG forever.
But yes, I think the chance for Mbappe to leave PSG is very low at the moment. But do not rule out the possibility that in the next few seasons, it is very possible for Mbappe to really leave PSG.
About Benzema, I think Benzema can be paired with anyone because Benzema is not a selfish player who scores goals.
With that style of play, of course, other players won't have a problem with Benzema. But unfortunately, Benzema is no longer young and this will at least make his recovery from injury last longer than normal recovery.
Also, if an old player is injured, then in the future this player will remain vulnerable to getting injured again and of course, this will be an obstacle for Benzema to be able to continue playing in every match later.