In metropolitan areas a smaller car makes sense but get into the bush or the desert and suddenly a large car is sensible - a lot of Australia is bush and desert. New car sales in general have and will continue to drop off in favor of used cars,though a lot of people are still willing to put up finance for a brand new car which by the time they end up paying off will be worth half or less than they had been paying all along - something which makes terrible economic sense to me and a lot more people are waking up to.
The Holden brand will not disappear because they sell all sorts of vehicles and have built a name/reputation, from a business point of view it would be a huge loss, though with government restrictions getting tighter and more expected from the companies it can be a bit overwhelming for them to keep up; next Commodore could be a very different vehicle to what we've known (shrinking, cheaper quality, hatch? Torana?!)