For me, Man City is still the favorite to win the EPL title, because Man City is only 5 points behind Arsenal who are in first place and the EPL league is still very long, not even half a season yet. You need to look at last season, before the middle of the season, Man City was also behind by a fairly large difference in points with Arsenal, but entering the 30th EPL League match, Man City was slowly able to catch up with Asenal in points to reach the top of the standings. At the end of the season, Man City became champions. Here are the facts
Regarding KDB and Hallaand, I read news that it is possible that in mid-January they will be included in the squad again. But what I want to say is don't think that Man City is unable to catch Arsenal because they are now in fourth position. Learn from history, they have a strong mentality, especially as coach Pep Guardiola can return to first place at any time.
Since Kelvin Debruyne absence alot has happened and it felt like some part of the team became exposed, giving other teams a chance to predict Guardiola's strategy, but with his arrival by January, we'll begin to see a very tough and brilliant City that scores alot of goals, it's going to be a big boost for them cause Haaland and Debruyne understands eachother very well.
Arteta has certainly learned from his mistakes last season, we can see this from his moves to add depth to the squad this season. If he gets sick again at the end of the season, it means that Arsenal illness is very fatal, difficult to treat even if they recruit more expensive players. Talking about turning points in performance, Pep is more astute than any coach in the EPL except Unai Emery this season, City can recover quickly if De Bruyne, Stones and Halaand are available again in one lineup.
On the other hand, City achievements last season could be one of the factors in their declining performance this season, apart from injuries to their core players. It feels like Pep needs to motivate his players more to be hungry for a winning record, and avoid feeling complacent and being lulled by past success. We will all be waiting to see how the transfer window will be used by the teams competing to challenge for the title. Pep seems to need to join in the hunt for players there.