I think what all madrid fans hope is that the number 9 jersey is more suitable for a young player like Mbappe but unfortunately Mbappe is still staying at PSG until the end of his contract, even though it sounds like he is not extending his contract with PSG it will wind up soon it looks like Madrid can take him , almost all the media reported about this.
To be honest, if Mbappe joins Madrid, then Madrid will be a scary club. Also, being able to compete in the UCL against Manchester City as the defending champion, as we have seen so far, Madrid has brought in several young players who have just joined Madrid, so I will be happy. see how the current main squad can compete in the domestic league including in other championships such as the UCL. still waiting for who will replace Benzema for this season.
From what we hear, Ancelotti is planning on making a diamond tactic, with 2 at the front, who will be vini and rodyrgo. Which means that we are going to see no pure striker for them this year unless they get someone and it doesn't look like they are getting any. Mbappe may join next season for free, that is a big possibility and I believe that if he actually does that then we are going to end up seeing the team change a lot.
Ancelotti doesn't plan on staying, he will leave after this season, so Mbappe will be someone else's player. With that in mind, next season there is a possibility that Modric and Kroos may not be there. So with all the players they have right now, minus modric and kroos, adding Mbappe, that would still be a world class team who will fight for a treble.