Pep's time at Manchester City was fantastic. I still think they will have such a good time. We will watch him in the blue City for many years to come. Because of Manchester United, the city of Manchester was red for many years and now it is painted blue. The person who had the biggest share in this was the club president and Pep, who made the best use of these opportunities. Frankly, I don't think he will retire anytime soon.
Pep Guardiola is an experienced coach who has a lot of titles in various clubs he has coached, especially last season Pep Guardiola succeeded in making Manchester City win the Treble Winners and maybe if Pep Guardiola leaves the club it will have an impact on Manchester City because of the club he has led for many years years are very comfortable with the system and coaching, the coach who will replace him will not necessarily have the potential like Pep Guardiola and Manchester City will have difficulty finding a replacement who suits Manchester City's playing style.
Same goes for Pep as well, even though City will have hard time replacing him as manager and find someone who can get them all those wins, they could spend more and more money all the time and test managers and eventually maybe get it again.
But, there aren't all that many teams in the world that can go for UCL, City is one of them, madrid, bayern and maybe psg if they are properly managed, there are very few clubs that can win the UCL title, and if Pep leaves City, then which team would he go to? That would be hard, if he goes to a lower team than these, then he is not going to win, and if he doesn't win then he is not going to be getting offers again from the highest UCL winner level clubs, so his career would go down. So he realizes that even though City would hard time, eventually they can recover, but Pep will not be able to recover that easily and he might have trouble, unless he goes to a huge club of course, then he will be fine too and stay there for many years.