JB was quoted last year as saying they wouldn't think about taking up the two remaining options until at least 2013.
Storm and then calm as Virgin Australia posts loss | CAPA
Of course many aspects of that article have been superseded as time has gone on, so you can certainly argue that JB's views on 777s could have evolved too. But even if they convert their options today, how long until the aircraft are delivered?
The 777s are stretched so thin at the moment that the only way to utilise them better is tag-on flights (either into Europe as that article speculated, or somewhere in North America, both of which seem unlikely) or to drop existing routes.