There's no point QF going to 777s now. The 787 is the right size to replace their ancient 767s, and they're getting the 380s to replace the 744s. The delay is bad (very, very bad), but to go to an older technology a/c may help short term, but stuff them long term. The 763s and 744s will have to do for now.
With hindsight, they could have gone to 777s, but they're too big to replace 1:1 with the 767s, and not quite what qantas would want or need to replace 744s, with premium pax to LHR and LAX/JFK, and with routes SYD to JNB and SYD-EZE not suitable to twins.
JQi could possibly be expanded now with A330s, but given current demand for them, how do you get soon enough delivery of new-build A330s? The only possibility for 777s is to go into JQi but that would add a whole world of cost and capacity that it's in no position to absorb.
With GFC, it would appear the correct course of action is to delay some 788s (and/or convert to 789s), get the 380s to sub for the 744s and then dispose excess 744s and/or use them on main trunk routes domestic +/- NZ routes (AKL) near the end of their lifespan (like the 743s were).
I'd say the 788s will end up with QF to replace 767s including possibly on domestic routes, 789s will initially go to JQi. Although i'd rather see them got all 789s (no 788s).