I think the stance with Pep and the board regarding Aguero has been clear from day one:
Pep and City won't be trying to sell Aguero anywhere. BUT if we do end up getting both Mbappe AND Sanchez, Aguero knows that Pep would put him 4th in the totem pole: 1,2,3 are Mbappe Sanchez and Jesus. Aguero comes after that. In that situation Aguero himself might not want to be the 4th choice player and look to leave. If Aguero himself look to leave, City will definitely sell IMO and recoup a huge amount of cash.
Now Pep and City has set this up so this is a win-win situation for them:
1. If Aguero leaves, they will maintain that they did not want to sell him and that Aguero himself wanted to leave and they had to respect his wishes to do so.
2. If Aguero stays and accepts his reduced role, then City will have a hell of a depth in the squad.
Whatever the outcome is, City and Pep will always come out as the good guy. And this is all because Pep and City have never wavered on their statement regarding Aguero : that City are not looking to sell him and don't forget Pep mentioned this so many times (I'm paraphrasing here) : If Sergio wants to stay, he will stay. Everything depends on Sergio. We are so so happy to have him in our team.