It's the best option the RAAF can get, especially avionics and capability-wise, it also makes sense with the current Hornet fleet and going JSF in the future. It's perfect for the next 5-10 years, especially for international commitments. Going French as interim solution until the JSF doesn't make sense. The air-to-ground Typhoon is not ready yet. The Typhoon probably has too big a lead time as well. The F-15E is probably too expensive. The last option I can think of would be advanced block F-16s. Don't forget it is a backup solution too. If JSF fails, Australia will order more Super Hornets.
It can be cancelled, at very high penalty costs, but not as high if it would have been a commercial purchase deal. Production is still running for the US Navy, so that won't be that big a problem.
I don't think it will be cancelled, maybe downgraded to ex-US Navy Block I's with the Navy getting the Block IIs, but if cancelled I don't think we'll see a 'replacement' solution at all anymore.
(Those Swiss Hornets are not designated just F-18 for no reason, it doesn't have the full attack capability, I doubt how much of the self defense suite is still there and what radar it has. Anyway, that's probably why it is lighter, less wiring, less components. I wouldn't give them credit for degrading a multi-role platform, the best there was for years, into a single-role fighter. They might as well have bought F-16 or Mirage 2000C then.)