If we get De Bruyne then Sterling, Aguero, KDB with Silva in behind is going to need a fully mobile midfield.
Pressure is on Toure. I have always thought that Fernando and Fernandinho were capable of forming the defensive basis of a 3 man midfield, but I'll be in a tiny minority on that. I think we may find out next season because Toure is really going to have to work hard in pre-season and get his fitness back to where it was 18 months ago.
I think Toure will find himself playing less games and he'll be a sub, but it's up to him.