According to Ausdroid.net:
According to sources, the dongles are both listed in the JB Hifi inventory system, with the launch expected to come within the next couple of weeks. The dongles are both slightly more expensive than the current $49 RRP of the original Chromecast dongle, with JB Hifi listing them at $59 each. The SKU's are in the system, with JB using 937278for the Chromecast 2 and 937282 for Chromecast Audio – both of which unfortunately do not show up in a search on their site.
The site adds that Kogan Australia is also showing "Coming Soon" listings for the new Chromecast and Chromecast Audio for the same prices, although the black version of Chromecast is shown as shipping in between 1 and 2 weeks.