Man City fans must expect this but I think it is unlikely to happen. If Mbappe joins Man City, he won't play in the striker position because Haaland is the main striker of Man City. Mbappe must be ready to play as a winger, he must serve Haaland. I don't think Mbappe wants do this, he must expect to be the main striker in his next team. He also must dream to be the main goal machine of the team. So, there is no way to play together with Haaland. It is still better to move to Real Madrid because he will play as the main striker there.
Sure, if he is in the same team with Haaland, there must be a competition to be most shining player there. I assume Mbappe and Haaland can be difficult to cooperate together because they want to score as many as possible. It will be bad for the team if the player become egoistic and play individually. So, it won't be a good idea to join Man City.
Out possibility with Mbappe will join Manchester City exactly he can't play as central forward because there are has Erling Haaland and Mbappe should play as winger position. In Real Madrid, he will priority become main striker and Carlo Ancelotti will put him in the central forward with left side fill by Vinicius Jr and right position have Rodrygo. For Manchester City don't huge expected with the dreaming team by signing Mbappe because he won't play on the same team with Haaland.
Betweeen Mbappe and Haaland as competitor and difficult each other will play on the same team, Mbappe want to show him self more better than Haaland and get winning more individual trophy in the future, Madrid will be good place for Mbappe because lack of central forward position and actually this position will be for Mbappe if reach agreement deal with Real Madrid.