Sunderland looked very good in their last match, They were 0-2 down and could have been a few more vs WBA, but managed to take the score to 2-2 before ht and missed many chances to score the winner. It seems that only worry is their defensive play.
The same can be said about Arsenal. What is important to note is that they have conceded vs nearly any team at home this season (only Swansea and Bolton didnt).
Sunderland palys better vs top teams so it can be right moment to face Arsenal when due to International games Arsenal team still wont be a 'team' yet. Especially worrying is their defensive play where are many injured players or new ones who cant as yet get used to Arsenal way of play.
Another factor for high-scoring game is Bendtner in Sunderland who shows that he is very good there - many assists, few goals. He will be very motivated to do well against Arsenal where he admitted wont go back ever again ( he is on loan at Sunderland).
All in all both teams defences arent at their top so it should be open game especially as both coaches and teams have a lot to prove after bad start to the season.