It is possible that the formation that will be used by the Arsenal team will not be much different from the previous formation because remembering that with that formation, Arsenal was able to beat Manchester City even with a very small score. But this time Arsenal must hope to win with more goals even though it might not be easy enough for Arsenal considering that the match is at Chelsea's home ground. However, Arsenal needs to hope for this in order to gain more advantages.
If the formation help them beat ManchesterCity and maybe some big clubs they've faced, then they'll definitely want to try it against Chelsea in their Derby match, onlike every other matches they've played this could be one of the toughest they'll play so far cause it's a London Derby and Chelsea are the home team, they'll use that to their advantage and might want to use continue impressing their fans since they're now gradually picking up, they suprisenly had a comeback in the match against Burnley and won with a 4-1 victory.
It would be difficult to chose which team to support if you're not a fan of both club cause though Chelsea would be playing with a home advantage, Arsenal are still favourites to win the game and are in a great form recently, they've got one of the best front three currently in the EPL and they could really trouble Chelsea's defense.