According to the rumours, Amazon Australia is going live tomorrow.
Australians are already buying electronic products from Amazon in Australia, and products from offshore, but having a warehouse locally is a big plus and having warehouses allows the retailer to cut delivery times and often costs. So it does not mean the end of the world. In the short term, I expect that Amazon will be coming out with low margin items to drive volume, in the medium term, they will be stressing their website, which is not yet up and running in Australia for the warehouse and in the long term, once they get organised, it will be delivery.
Based on what I read in other countries, this is going to be a huge shakeup. A qualitative change is now underway in Australian retail.