Because mbappe declined to extend his contract with PSG, many people believe that Real Madrid will sign him. This leads real Madrid supporters to believe that mbappe will join their team, but according to the rumour I've heard, nothing can be done once mbappe accepts the offer from PSG because money can buy anything.
I've also heard rumors that Kylian Mbappe will leave PSG and sign with another team, but since PSG doesn't want him to leave, I think they'll offer him a lot of money in exchange for extending his contract with the team. If I recall correctly, this happened before when he wanted to leave and they offered to pay him more than he was earning, so he stayed, which led me to believe that Mbappe will still play for PSG this time around because they will offer him alot of money and PSG is a wealthy team they have the resources to make Mbappe stay.
Even before, I thought Real Madrid would sign Mbappe to their team because I believe Mbappe will fit the team, and I also think when we want to talk about some weak positions of Real Madrid for the last season, the position Kareem Benzema left now will be weak the following season, no doubt about that, so I think if Mbappe gets in there, I believe their squad will be more stronger.