I think his legacy is indeed damaged, and the longer he stays in the game, so much more that is going to be reaffirmed. And I think the damage he has brought onto his own legacy is so great and irreversible that it will actually shade over all of his accomplishments and contributions to the club and football in general, casting doubt and questions over whether what he achieved wasn't actually indeed just chance rather than any form of ingenuity.
Yes, he will be remembered as the manager who, if ended seems too strong a word, at least challenged and rivaled Man United's undisputed reign over English football in the 90's. The manager who changed the English game forever. But thanks to 11 years of stubbornness and obscurity, you have to ask yourself the question whether it was indeed Arsene who brought change with him, or he was simply a symbol of change, the right person at the right time in an already evolving, globalizing world, of football including.
There is a saying that goes something like this: "Intelligence is the ability to adapt to change". In that accord, Wenger is a stupid, stupid man. And that stupidity of his, i.e his absolute inability to change and adapt to the modern game, gives enough reasonable doubt to question his greatness back in the day.
What Wenger achieved with this club will always stay and be remembered. But how and why he achieved it is now under scrutiny. He will be a fool to stay in the game come the end of the season, but that is exactly his weakness, his foolishness and self-believe, which is why I fully expect him to sign on or at least move to another club, where, in my opinion, he will only reaffirm what an outdated and lacking manager he is.
The fact is that we have reached the tipping point where he is already unwanted, and only fools stay where they are unwanted. When unwanted, politicians resign, husbands divorce, and football managers should quit. Hopefully Arsene has at least as much common sense left in that old, senile head of his.