I don't think that Arsenal will be able to hold on to their performance until the end of the season because they don't have that much squad depth. Manchester City really lacked a lethal striker for the last few seasons after Sergio Aguero left. But now as they have bought Erling Haaland, they will really try to push for the Champions League title which they have been wanting to win for the first seasons but were unable to do so.
So far Haaland has shown what he is capable of as he scored 10 goals in only 6 matches. So far Chelsea and Liverpool have been playing their game this season so Manchester City might have a really good opportunity to grab this and be the best team in England and possibly Europe.
If for any reason Arsenal will be unable to maintain this form to the end of the season it will be because of the lack in squad depth cause the players have the spirit and zeal to fight hard and win games, they have showed a lot of improvement in their performances and I think if the club is unable to bring in new signings to support the ones they have already the available ones will burn off and suffer fatigue.