It will not be so hard for a club that has won treble winners to find replacement for him. The main problem if it will be very hard to get a player that can adapt to the manchester city as good as silva.
The fact that if silva has been always contributing a lot to the club since a few years ago once he was coming to the manchester city. It will be so difficult for pep to let him go at this moment caused by he has become one of main players in the club.
City gonna be very hard in finding a new player that can adapt to the club like him. That's why city shall have done something better in securing him from another club.
It's difficult to say about the future of Bernardo Silva, sometimes Pep Guardiola says the opposite for his players. He is an important player for this club, and we really need him, after a few days the player in question left the club. Maybe Pep is acting like that to maintain the mentality and concentration of other players so they don't get distracted by the transfer market.
I think Man City, especially Pep, will have no trouble if they lose Silva, because there will be many other players they can easily recruit. But in line with what you said, sometimes the adaptation process will be the biggest challenge, especially since the EPL is very competitive every season.