Kelpie, I really hope you're wrong. Unfortunately, I can see it playing out just like you predicted
Future 'Virgin Australia Cadets' will not be employed by the mainline domestic 737/ejet business.
The FAQ page on the Virgin website sort of covers this (unless this is referring to Skywest's jets):
Am I bonded for a period of time?
Following an offer of a permanent role post training you will work for Virgin Australia in partnership with SkyWest and will be bonded for three years. Should you be successful in gaining a role on the Jet operation with Virgin Australia after this time you will be bonded for an additional three years.