Voz is an independant company.
To operate on SYD - HKG would mean they are directly competing with another Virgin carrier. It is not a particulally successful route for Virgin Atlantic either.
They are fully aware they would lose the battle, when V Atlantic can offer a far superior product, for what would be a similar price.
The USA is a market with few operators, where they can successfully brand themselves as the only alternative to Qantas.
To Hong Kong they have to compete with Virgin Atlantic, Cathay, Qantas, British Airways etc.
I think they'll stick with their current plan!