The government debt guarantee will be very limited. QF will have a limited bond issue with a gov't guarantee (and a handsome interest charge). The taxpayer will not be liable to all QF debts, and the government will probably do quite well out of it.
What is of concern is what QF do with the capital raised from a gov't backed bond issue. Will they be able to use the money to back further Asian adventures? As economically illiterate as Tony Abbott is, I can't see a gov't debt guarantee coming without very specific conditions. Why do you think Virgin are so "me too" about a gov't debt guarantee? The money will have to go to investment in Australia. It might just be what saves many Qantas jobs and provides investment onshore.