I rate Yaya Toure very highly, maybe one of the best in the world at his role.
I'm one of the minority on the Caf that rates Milner quite highly too. Milner can do a great job in midfield if he has good attacking players around him.
Silva is a tricky one, I think under the right management and in the right system he could be extremely effective in creating good attacking football. Silva along with Tevez could turn out to be a hell of a partnership!
The part they need to improve on is the quality of their wingers and if they do get Krasic (which I don't thin they well considering the apparent reaction of the player when heard of City's interest) then they could easily challenge for the title with that team.
I do rate Adam Johnson, he has great potential to be a top winger. He seems to have a good footballing brain and some feet on him, he seems to be a type of player who can grab a game by the scruff of the neck.
But the fact of the matter is, City are going to get better, and whether it be next season or not, they will eventually be up there challenging us for the title.