Keeping the same squad will not guarantee the success of the team another time, that's sure since all teams are changing players, coaches, management and tactics. The old players are getting older, there isn't a lot options for using them and giving some changes while making the team younger will guarantee success on the long run eventually. Guardiola know that and he is trying to keep keys players while giving younger ones a chance to play with them.
Pep Guardiola is a coach who is a genius at making decisions so he is already thinking quickly about what steps to make after releasing players in this transfer window. I agree with you that the team will not always use the services of old players so that regeneration is carried out gradually to balance the team's strengths in each season.
Mahrez already an aging player at 32 years old and Pep Guardiola will be looking for younger players in this transfer window. The strength of the Manchester City squad is still quite strong despite the changes that have occurred in their squad. We will see what the transfer market will be carried out by Pep Guardiola to find the right replacement after Mahrez leaves. Mahrez has found his best form after he joined Manchester city from Leicester city where he has won many trophies and ucl trophies. So he will decide to leave the European stage by joining Al Ahli next season.