A "AirNzAus" or a "SilkAus" are extremely unlikely. Both owners of those brands got bailed out by their governments, and Silk is being absorbed into their mainline SQ brand.
Also to add both companies' previous attempts in the Australian market had ended in dismal failures.
SIA (Singapore Government) or Air NZ (NZ Government/NZ Investors) aren't that stupid to have a 4th attempt (or 3rd attempt in NZ's case) at the Australian market.
Especially when pointing out the incompetence both SIA and Air NZ had when they had full 100% control on one of their Australian attempts (For SIA that was Tiger Airway AU and Air NZ that was Ansett), and yet still couldn't get that attempt right due to a mixture of incompetence and egos.