More likely will be that some of the 787-8s from JQ will transfer across to QF once the neos get going in JQ and take over the runs to Bali. At that point, they might decide that JQ steps out of widebody altogether, and the -8s supplement or replace the A330s into Asia. It was always intended that the -8s at JQ would be replaced by the -9s that offer lower CASK and greater range, but the way they are deploying the -8s now tells me that the idea of longhaul low-cost dominance is out of favour.
Whilst I think you're probably right, at the last roadshow Salter was adamant they are making a business case for more 787s at JQ. Make of that what you will.