It’s not necessarily holy writ, but an unofficial list of all the Samsung Galaxy S 4 variants suggests that the Australian model will indeed be the quad-core Snapdragon based unit.
The list, compiled by Sammobile, states that Australia will see the GT-I9505 variant of the S 4 rather than the GT-I9500 Exynos version. Some countries will see both versions of the phone, including the UK, which was tipped to only get the quad-core version just yesterday.