Ordinarily, Pep Guardiola wouldn't allow a player like Kevin de Bruyne to leave despite the reoccurring injury problems, I think it is the player himself that is insisting on leaving the team, I think the player believes his time at the Etihad is over and perhaps it is time for him to leave the club, his wealth of experience has been duly utilized at the club and the evidence thereof are too numerous to mention because Kevin De Bruyne is one of the most fulfilled player in the Manchester city squad at the moment hence he has nothing to lose if he leaves now and for me, I think his decision should be respected.
I don't think I would that certain if I were you because if there is one thing I know about guadiola that would be the fact that he doesn't really work with players that are turning out to be liabilities and despite the fact the Kevin de bryune is one of the core players in the squad if injuries and other set continue to hold him back I think he would have no choice but to actually adjust and find a replacement for his role just as he has been doing over the years.
Gardiola could be said to be that manager that Don hesitate releasing off players from his team that have advanced well in age seeming to turn to liability to his squad but in the case of KDB, Kelvin despite the recurring injuries doesn't look like a liability for City as he has always being phenomenal on every return from injury helping the team win important games, which doesn't in anyway makes him look like a liability for his age.
And if we're to look at age İlkay Gündoğan is one year older than KDB but still have to play for city next season, so it's much likely it's KDB decision to leave the club next season and not thay Gardiola wouldn't want to keep him if he had wanted to stay.