When it comes to Nintendo, as with most gaming matters, European and Australian release dates are often in-step. Sometimes they're the same day, other times within a few days. So if Europe's getting the silver DS, it's safe to assume Australia's not too far behind, right? Haha. NO. Nintendo Australia have told us that:
We have no plans to release the Silver DS Lite in Australia at this stage.
Bummer. Doesn't mean it's not coming, just means we shouldn't expect it in October.