Make no bones about it, Rodri missing for the season is a huge blow to City.. RIght now they have who? Kovacic? He's not the same player. Rodri is (unfortunately) one of the best in the world at his position, and as others have said, City are not the same team without him. Add into that De Bruyne's spotty fitness the past 2 seasons, and you have a team that will struggle a little bit more at controlling the midfield. They lose a lot with those 2 players missing.
Now, will City go out and buy someone in January? Probably, unless they are going to get hit with all these penalties from the allegations. But they could drop more points by then. Now, they will win against teams like Fulham & Soton, and they have winnable games until the end of November. But then they have Spurs (Nov 23), Liverpool, ManUtd, Aston Villa (all december). I could easily see them dropping points in more than one game between now and January.