[Note the information below is relevant to Fibre to the building only, this article is due for a rewrite]
Seeing as neither myself or a single one of my customers has access to that mythical telecommunications product the Australian NBN I haven’t bothered about this in the past. However I was specifically asked a modem/router future compatibility question a couple of days ago and I did some brief investigation and came back with this information, I have highlighted the main thrust of the info below:
Bit.com.au says this:
An “NBN/fibre-ready” router means that the model [has] a Gigabit Ethernet WAN port, which allows for fibre or cable connections.
PC Authority says this:
In an NBN equipped household the NTU effectively takes the place of the modem that you would currently use for ADSL or cable internet. This means the death of the commonplace modem/router hardware – moving forward you'll just need a router to spread internet around the home. At a base level this means that ‘NBN ready' modem routers have the capacity to disable the ADSL modem and take an internet signal directly.
The potential issue with such devices is that the hardware is designed around low ADSL speeds and may not actually cope with the demands of the highest end 100Mbit down / 40Mbit up NBN speeds. If you aren't going with this high end plan then router performance is less of an issue, but it is best to think of an ‘NBN Ready' ADSL modem/router as a transitional technology at best.
TPG have a good diagram here:
I also found this useful FAQ on the NBN: