With Manchester City still their competitor, they cannot be said to be champions yet. Their points gap is not too far and the Premier League still has enough games to make their position change. Arsenal just need to maintain and continue to gain full points if they want to become champions. Because now they are depending on the results of their own matches with them leading the table at the moment.
I believe Arsenal have more chances of getting the premier league championship than Manchester City. The premier league title is the only title Arsenal is fighting for right now, with this as a main target for the team it is very possible they will eventually achieve what they want. The gap in points between arsenal and Manchester City is a big advantage for Arsenal to win the Championship. Manchester City has good squad which won't be easy for them to be at the top of the league. What Pep Guardiola is mostly concerned about is the Champions League and that is what his players are trying to get.