There are a number of reasons why it is being held in Brisbane.
First and Foremost is probably that the guy who arranged to use the rights etc of GENCON lives in Brisbane.
Also in my experience Brisbane actually has one of the most vibrant gaming communities in Australia.
In the last few years there has been a bit of contraction in the number of stores up here but I would still say that there are probably still more gaming venues/ Stores in Brisbane than in any other city in Australia.
IIRC from my dealings with Store owners/distributors more material is sold in SEQ than in Sydney or Melbourne
Alot of the nationals for some minatures/CCG comps have been held up here as part of Conventions or as standalone events.
The May convention up here NONCON/ The Big Weekend (as it has been known) would regularly get 500+ attendees - I have seen simultaneous 30+ people Warhammer /Warhammer 40K/ DBM convention events
I know that at Gencon there are expecting 25-30 Warmachine players and would love just a few more to hit 32.
Unfortunatley I can't go due to family/work commitments otherwise I would have been there running 4E DnD
