It was in the past that we do use past record to predict the future, but this season proved everyone wrong that past history doesn't guarantee future results. I see Chelsea as the favorite in this match, because City have lost form and are unpredictable when playing with big clubs. Imagine how they lost their only chance of qualifying to the round of 16 to PSG, despite on two goals lead.
This weekend's match will be very tough for Manchester City because Chelsea are a very different team from last season and what you said is true that this season all teams have experienced a difference in performance, both those who were good before and are now good, and vice versa as we saw together with one team, Manchester City. I also don't think Chelsea will give up easily when playing at Manchester City's home this weekend because Chelsea also really want to maintain their position in the top four zone so they will try their best to win at Manchester City's home.