The good luck on them is the fact that while they have lost good strikers they had, they are going to have a shot at Mbappe. He basically said he will not renew his contract with the team and PSG is not willing to let him go for free, considering he is one of the best player of his age, PSG will want a ton of money to sell him and there are very few teams who could pay for it.
The sudden departure of Benzema increases the need to buy a new striker in Bernabeu. Perez publicly answered that he and Real Madrid open to buy Mbappe but not in this season. It sounds logic because if they wait till the next summer, they will be able to have Mbappe as a free agent because Mbappe rejected to prolong his contract with PSG. PSG don't want to lose Mbappe without anymoney from transfer so they announced that they are ready to sell Mbappe.
The question is just the cost of Mbappe on the transfer market and will Real Madrid be ready to spend hundred of dollar to buy him when he only has one more year in the contract. I believe that Real Madrid have enough patience to wait one more year and save a lot of money.
I am not expecting City to end up paying it, United takeover is still not done yet and we are talking about Real Madrid here, it fits so perfectly because they have no striker and can play Mbappe directly at striker with no competition and he wanted to play there since he was a child, it's a perfect storyline right now and could be amazing to see.
I don't think Pep Guardiola wants to have Mbappe because he needs players who can follow his guide and he really hates players with high ego like Ibrahimovic or Mbappe.