Considering how many flights EK, QR, SQ and others are flying daily, I would say yes, as long as QF can have a point of difference.
Sunrise services will be in their own category and will have a price surcharge associated with it, PER is already operating without much feeder traffic from the East.
SIN will be the only flight for East Coast pax that want an intl stop and/or not pay the sunrise surcharge, so I expect will remain popular. Perhaps yes it will be downgraded to A350 (if they want to retain F) or 787.