Wenger leaving would not be as simple as a managerial change at other clubs. He's been in place for two decades, and is basically the last manager to be in the same role at a big club for that length of time.
Arsenal is set up for one man with vast experience and knowledge of the club to be its manager, and is not set up well at all for a manager transition. Nobody in power has ever hired a manager at a top level league before, as far as I can tell. There's no director of football and no sporting director. Wenger is in absolute charge of every footballing detail. If he leaves, then several people will have to be hired for important roles. And who would even be the one to make the decision on who to hire for those jobs?
From
The Short Fuse:
"Arsenal do not have a Director of Football, and do not have anyone on the
board really suited to fulfilling the role, hence making an external appointment a necessity. Ivan Gazidis is perhaps the closest to the position, but as Gordon Smith
explains, the director is really a football pitch related job:
The person who goes into that job actually has to operate the strategy of the club...You're looking at a medium to long term strategy. What you're looking at is to say 'OK we need to put things in place; the club in general has to run in a certain way'. The first team will still have a coach and there will still be pressure on the first team manager to deliver results. But other than that, you need to put something in place for the club as a whole in terms of youth development and the scouting department and everything to do with the media and all that sort of thing so the club runs in a very clear and good operative manner."
From Arseblog:
"There’s a lot more to the changing of the guard at Arsenal than one man in, one man out. You don’t replace Arsene Wenger with another Arsene Wenger. The structures at the club at this moment in time are a long way from what’s required to bring in a modern day head-coach. The almost total dearth of football and Arsenal knowledge on the board that has to be addressed, because if it’s not, the decision-making will be a long way from as informed as it should be for something like this to happen.
Make no mistake, it’s seismic. It might get worse before it gets better, but you’d be hard pressed to make the point that it’s going to get better under the manager as it stands. But we’re in this weird kind of limbo right now where the board would like nothing more than for him to sign a two-year deal, and until the man himself makes the decision, nothing is going to happen."
As said above, Wenger is the one who will decide if he comes back next year, not the club. The team has offered him a two-year deal already, and are letting him decide if he wants to sign it. That pretty clearly shows that Kroenke's preference is to bring back Wenger. Kroenke just wants to keep the money rolling in and seemingly is just fine with the status quo of top 4 finishes with no titles, and Champions League qualification every year and then getting knocked out in the Round of Arsenal. He doesn't want to risk that by making a managerial change. The decision will be Wenger's alone.
Wenger leaving would have a big impact on the players as well. One reason Ozil came to Arsenal was because he would be allowed to play a free-roaming, little defending role under Wenger, and he
has said that his future at Arsenal depends on Wenger staying:
"Özil, who signed for
Arsenal in 2013 after three years at Real Madrid, said it is not a financial decision: “The club knows that I am here most of all because of Arsène Wenger. He is the one who signed me and he is the one whose trust I have. The club also knows that I want to be clear what the manager is going to [in the future].”
If Wenger leaves, Ozil may well want out too.
Sanchez may already want out, but even if he is not at that point yet, if Wenger and Ozil leave, he surely will want out at that point.
If Wenger opts to leave, it will cause a huge vacuum at the club, the two best players might well follow him out the door, and the club does not seem at all ready to bring in the several key replacements they will need.