If Qantas gets both slots Aus-Japan capacity remains about the same. One 747 out, 2 twins in, Mel service moves from NRT. If VA gets one the capacity increases. More tourism both ways.
In a market with an additional slot each for ANA and JAL, Virgin could only thrive in a tie up with a Japanese airline. JAL is deeply in bed with Qantas, so that leaves ANA...