Manchester city has paid the price long time ago, they over spent in building this team, even if they don't buy any players, they have enough bench to use, they are not lacking players. and they don't need to buy much as if they are building team. Pep has to fill in space of the players that are due to leave the club or the ones they have sold out.
they have made English football entertaining, and feared by others. they are now the only giant of England. next season, they want to retain the Champions league and i see no club to stop them.
Manchester City already has depth and I don't see Pep having problems as a result of a couple of players leaving the club. Although, they have lost a top quality player like Gundogan to Barcelona, Kyle Walker is reported to be at the verge of joining Bayern Munich anytime soon, and Mahrez is also linked to a Saudi Arabian club side, but the team is still solid. Pep has done well to re-reforce his team by acquiring Mateo Kovacic from Chelsea, and working on deal to bring in Benjamin Pavard From Bayern as Kyle Walker's replacement and Josko Gvardiol from Leipzig.
It does not matter if only a few key Manchester City players leave because after all, these players are also old and ofcourse Manchester City should do and or prepare to regenerate the squad. Say also like Sterling for example who has left first, which basically at that time Sterling was also the first choice in the Manchester City main squad. But in fact we can see and judge for ourselves, Manchester City under the coaching of Pep Guardiola is able to continue to make a great and disciplined squad. So, there does not seem to be any problem for Manchester City as long as their head coach is Pep Guardiola.