I think he should stay in Milan because he has achieved something with this team at this stage of his career and I believe it should be memorable for him. But we all know and agree that ibrahimović is a different type of character. So, I am not going to be surprised if he decides to play for any other team. It is going to be interesting to see when he is going to retire considering that he is really old right now.
He gets paid 7 million euro for basically not playing. He didn't play that much this year, he is going to miss out next 8 months, and he will not be %100 when he comes back neither, so that would be another 7 million as well. I know that they became champions, but just because they got some money doesn't mean that they should spend it like this. For 7 million a year, they could have found someone that would be more ready and playing. Even if that player turn out to be not as good as Zlatan, which is a hard thing considering he is 40, I am sure that you could find someone for 7 mil a year that would be ready for all games, even if on the bench.
Maybe I'm not quite up to date and a little behind the times, but it seems that there was no talk of any 7 million for the next season. Moreover, due to the operation, Ibra seems to lose 7-8 months and therefore will not receive this contract, as if he still spent a full season.