Donnarumma is a diehard Milan fan.
His entire family are Milan fanatics and hes spoken a lot about how he only ever wants to play for Milan.
Obviously that doesn't mean he will stay there forever - he's only a teenager after all - but right now he's starting for his childhood club at 17 the fans adore him, he's been anointed Buffons successor for italy and Milan are progressing as a team while he's still cementing himself as a senior player after about 50 professional games.
Milan even have billionaire owners so there should be enough money to go around and the promise of returning to former glory.
If this one is true, I think it might be one for at least a few years time. He might get restless if they still aren't back winning things and competing in Europe by the time he's 21 or something.
Besides god forbid how certain fans would react to him making any mistake here.