Well.... he won the league in his final season. THeir dominance was ended by the influx of gigantic sums of money but I dont think you can argue that they were overtaken until he left. THe extent of that shows the full effect of his departure.
Now they spend a fortune and are not able to catch up.....
I've read a detailed review of the Champions League match in London at http://www.arsenalnews.org/ and made a conclusion that Wenger will continue to coach the team simply because he guarantees some stability. The Gunners' owners do not want to repeat the Chelsea's history before the arrival of Antonio Conte or an incredible story with Leicester in the 2015/2016 season..
My suspicion is that the 2 yr contract was decided upon as follows:
Year 1 - Find a new manager to coach the side and suitable replacements for all the extra tasks Wenger was supposed to be doing by quite clearly f ucked up because of his work load.
Year 2 - in case they don’t get all their chips into play they have the safety net of Wenger....if everything is sorted then thank you, goodbye and an extremely generous payoff.
I’m guessing the age discrimination card is just an attempt to max out his final payout from us.