The A340-500/600 was overpowered from teh beginning with poor cruise SFC, Airbus was too excited with the climb performace to lock at the poor SFC, when the 777-300ER cames it was dead.
So Airbus needs to fix the mission cost quickly on a pretty modern aircraft, the GE GEnX for the 747-8 would with minor changes as removing a booster stage and adding a 0 stage to the HPC with a revised Fan frame do the trick, this quick solution could also be a mid-life update to the A330 series, with GE Capitial buying up the RR Trent 700 and PW4168A fleets and reengine with a GEnX-62C2 hence getting their money back pretty soon hepefully they can derate this one to the 56K required without loosing too much cruise SFC as RR did, Bypass ratio and Burner pressure does the numbers.