For record sake and to say, Manchester City is very complete in their squad, even if Sterling and Jesus leaves the club there is still right wing Mahrez, central Haaland and left wing Fodan to take the lead. Other good players including Grealish is still in the team. KDB is always there for reinforcement.
The issue I'm seeing in the squad is the alleged departure of Fernadinho, if the movement is to happen, Manchester City will need a good defensive midfielder to scale the season.
However Manchester City need players to be back-up, they can't always play main players because of the busy schedule. Especially if their main player experiences something unwanted.
Regarding midfielders, yes they have to strengthen in that sector, because if I look now that sector is not fully ready. So they have to find players who can fill the void they have.