The ageing of important players is a problem for all clubs including Manchester City. We felt that keenly last season with the departure of KDB, Gundogan, and Walker. Their time was up and everyone knew this. City dealt with it quite well imo. Some said we should have replaced them earlier but that would have been really difficult to do.
Last season, Liverpool made a major mistake in extending the contracts of Van Dijk and Salah. I made that point at the time when most of the football media was claiming this to be a football triumph for LFC. This season, the consequences of their error of judgement are there for all to see.
Man Utd have a similar problem looming in the age and contract of Bruno Fernandes. He is 31 and will be 32 next season. Man Utd are a famously unsuccessful club, but to they rely hugely on Fernandes. Take him out, and they will be in the relegation mire. In the last week, it has become clear that Fernandes is looking at moving away from Utd at the end of this season, and that this might also suit Man Utd because of the player's age. He might still command a transfer fee this Summer, but after that, probably not unless something aphysical happens.
I am not expecting anything to happen in the January window but this is a looming problem for Man Utd. They may treat it as an opportunity but their past record suggests that they are very poor operators in the transfer market.