This page will tell you when the NBN gets to you:
http://www.nbnco.com.au/when-do-i-get-it/rollout-map.html
Bear in mind that the new Government made a pre-election promise to dramatically change the rollout of NBN, (fibre to the node rather than fibre to the premises). If that's the case then 100Mbps ain't going to happen! See this http://nbnmyths.wordpress.com/why-not-fttn/ **DISCLAIMER - I just googled that, it may be a politically driven page. It seems okay from my skim read, but I don't claim to be an expert.
What can you get on ADSL2+?? In Australia, in my experience, you're always better getting a data capped plan from a decent provider (I've had excellent experience with Internode) rather than going for an 'unlimited plan'. Those unlimited plans tend to put your data at the lowest priority which means you get screwed at peak times. I'd always take a 100GB or 250GB, or whatever you think you need, plan over an unlimited plan even if it costs more and seems counter intuitive. Most of the cheaper providers also save costs by de-prioritising your traffic, so again, at peak time if there is insufficient capacity (which is often the case on cheaper providers), you get screwed.
I've got a number of premises and businesses running at 12-16Mbs ADSL (with 2Mbps upload) and found that pretty decent for most things.
I am very lucky however to have snagged a NBN area (Fibre to the premises), on a 25/5 plan, could go to 100/40 for an extra $20 a month, but it aint worth it for me.
Such a shame IHMO that they didn't stick with the proper FTTP rollout.