Well he still be coaching them when they reach their potential?
would be sad to see him go before that, nut what he needs is a solid CDM, which for me is what made Arsenal great in the past season.
A attacking team like Arsenal always need someone who is willing to drop back when everyone is forward and dictate play in the back third of the pitch.
Viera, Flamini etc and now they have 4 attack minded Mids, 2 fast fullbacks who go down the wing (fully) which leaves the two defenders opened to attacks. Now what the CDM would usually do is pull back and cover where cover is needed.
So for me the weak spot for Arsenal is CM or more so CDM.