In the selection of a type for point-to-point hub-busting routes the B787 is a better size over the A350 - especially for developing new routes (not to mention the particularly good price that Qantas negotiated for the B787).
In the selection of a type to replace the B747 AND A380, the B777-9X is a clear winner over the A350 due to being bigger with lower seat mile costs. An indication of this is the fact that Emirates (which had a huge input in the design of the A350) has cancelled all A350 orders and became a launch customer for the B777-9X (with a massive order).
When you throw in some engineering commonality and flight deck design commonality (with a probable dual endorsement), it is hard to see QF having anything but those two types in its International fleet in 10 years time.