Maybe the Dutch colonise us.
Could see something like the Omani's in the north-west, dutch in the south-west, french in the south-east and then everyone working there way up from there.
The Omani's (Qaboos) if they where to come would go to the north-west cause lets face it, there's a reason we don't have any major settlements there, its too damn hot. It may suit them however. However what they will do up there is beyond me.
The dutch in the south-west makes sense. I could see that south-west corner of the state being where their major metro areas are (could see the main settlements from otl Geraldton to otl albany) and even along the southern coast since its pretty moderate relatively speaking. The South-west corner is green and whilst looking relatively small, is still at least 10 times larger than the netherlands itself. Also it wouldn't be an english enclave like otl (no seriously, poms outnumber aussies in W.A). I think that corner will be where 90-95% of the population would live (i mean its still a 200k sq km + region, so its very big) and would sustain a good population (maybe up to 10 mill). I imagine between that and the east indies it becomes the major colonies for them.
The French where snooping around Tasmania (they landed before the brits i do believe) so them settling the south-east corner if things go to plan isn't unreasonable. If that research trip to Tasmania ends up being a colonising one instead, perhaps they could end up taking the south-east (meaning Melbourne is french).
As for the rest, who knows if the British don't come here. I have a feeling one of the other colonial powers (that aren't Portugal or Spain cause i can't see them getting to the east coast) will colonise the place eventually (further north), until then i see it being a power struggle between the existing colonial powers until they settle on borders.