We have to remember that we didn't have a clue who Wenger was when he first came here, so reputation won't guarantees success either. There is also the likelihood that we could go through a Utd style dip after a manager leaves after being in place for so long.
The other issue to face is that Wenger is likelly to stay on at the club in one capacity or the other, so his influence will still be felt around the club for some time after I think.