In principle ATO are interested in money turnover. That is money comming prior to any deductions (eg postage). The postage is now included in reporting mainly because the mechanism is now in place by Ebay to record it more easily. It was excluded before simply because it wasn't processed via the Ebay system. 

Will this boost number of sellers having details given to ATO? Yes. But ATO will still only be auditing the same number of people. They just have a bigger sample to pick from. This may mean they will be able to pick up more obviously dodgy sellers rather than less dodgy ones. Keep in mind it will not just be Ebay activity alone that will get sellers on the audit list, it will be only one component in the deciding factor. Unless of course you are selling thousands and declaring nothing.

I still reckon that threshold is just a "shot across the bow" to let us know they are watching.

I wonder if your paypal account will ever be reported to ATO? Can't see how, but never say never.