A new manager will get nowhere near that kind of money to be honest, the club aren't going to pay some guy 7 million a year to manage the club once he leaves, no unless he proves something, the issue here is that Wenger is basically happy with the setup I think it would be hard to find any half decent manager with the same attitude.
Benitez is a short term stop gap, everyone knows that, Chelsea couldn't get the man they want now so they got him as he was available.