Australian (and pretty much all) Discworld Conventions are bi-annual (i.e. every two years).
The tradition seems to be that even-numbered years hold the International Discworld Convention in the UK, and the odd numbered years have conventions in Ireland, Australia, USA, Germany, and the Netherlands.
There will indeed be an Australian Discworld Convention in 2019 - Nullus Anxietas 7 - April 12-14 at the Mantra Bell City, Preston, Victoria. More info and tickets are at https://ausdwcon.org - over 230 tickets currently sold, so it's even bigger than Nullus Anxietas VI!
Sorry for not posting anything here before - I'm only the website guy, I'm not in charge this time or doing the publicity or anything. Plus I think Rath and myself are about the only Australians who use this forum anyway...