The genie is out of the bottle now.
If Qantas sells Jetstar, it'll be to cashed up foreign buyers. More than likely the Chinese. These guys don't play the game on short term outlooks and quarterley statements. They play with the next generation in mind. What's best for china.
One thing is for sure, there will be no more protection of Qantas on its highest yielding routes. Jetstar will crush Qantas. It has a cheaper cost base and if it goes upmarket and even rebrands it'll be a big headache.
If Qantas keep Jetstar, it'll probably crush Qantas too.