North America generally seems like an obvious target.
I doubt Joyce will be too keen to venture into Asia, again, after the many experiences with the various Jetstar incarnations. But that is another obvious place to look, if only to increase frequencies to cities already served from Sydney but nowhere else.
The other possibility is increasing frequencies into Europe via Dubai on behalf of Emirates. Emirates are getting pushback now whenever they try to get slots into hubs where they compete with the legacy carriers.