I think the England side is also an example of what good coaching can achieve. They were quite poor under Lancaster at and before the 2015 RWC. Since then, with virtually the same roster, under Eddie they've risen to No 1 in world rankings (at one time), a record 17 wins on the trot, and have now put the Wallabies to the sword - the same team and coach who bundled them out of the Cup 4 years ago.
We have every right to expect that we'll see a similar improvement in performance as soon as Cheika moves on.
There'll be a bounce, there nearly always is. And we can hardly get worse. I hope.
If we want to see a sustained improvement, a LOT more needs to happen besides getting a new coach. Sure, we can look at the U-20s and Schoolboys beating NZ this year, but looking closer at what is happening in the de facto development pathways at school and junior level, there is a looming problem. Club rugby is enjoying good following, but the next tier is a bit lost.
England have a depth of resources (financial and human) that we just don't. We need therefore to be smarter, not just at the Wallabies level but all the way down. The current RA board probably won't fix this. They're as much a disaster as Cheika. But the whole pathway development, mainly in coaching structures (S&C, skills, tactics, kicking, leadership), has to evolve.
Historically, a winning Wallaby team can initiate some top down interest. I hope the next coach gets this bit right. I hope the admin gets the rest right.