There is a more epic coach on the market - Zidane. It's Mr. "Get the Champions League as many times as I want". I think one way or another they will be able to persuade him to lead the City. In addition, Mourinho seems to be regaining the status of "special one" and if he spends this season with Roma again successfully, then they can invite him. I'm sure the sheiks won't wait forever and give Guardiola endless chances.
Zidane is definitely one of the winner managers in the world. Just look at this record of him with Real Madrid in the Champions League I mean

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There is no guarantee like he would make Manchester City champions there many times of course. But I don't think that Zidane would have a big problem on winning it at least one time when he has an amazing squad like Manchester City have in his hands. I just wonder how deeply he would change the current system of Manchester City. Because Guardiola has brought these players taking his own system into account. Zidane had a way different system at Real Madrid.