Arsenal's weakness for the past three seasons is inconsistency. They were close to winning the English Premier League two seasons ago but they slipped close to the end of the season. Considering their present squad they have the capacity to win the league but they also need to get more players this January to avoid what happened to them last season when they had to manage players. But their ability to win the league will also depend on the performance of both Liverpool and Manchester City. Now the Gunners is four points below Liverpool and three points below City. So they will have to pray that these teams lose games, to enable them to overtake them. As you rightly noted the league is still young and open to almost all the five top teams. It will take only a soothsayer to predict which team will be the champions this season.
Player injuries have been a problem for Arsenal almost every season, and this season they seem to have a new disease, namely often getting red cards. If these two things cannot be overcome by Arteta, they will be the main obstacles to success, apart from their need for a qualified number 9 striker.
In my opinion, Arteta should prioritize the Premier League first, stabilizing the team in every competition will make them lose all opportunities like last season. Meanwhile, we have to admit that Arsenal are starting to look able to cope with the pressure, especially towards the end of the season, what is certain is that only time can answer whether they will be successful or not this season.