^
Considering most 747-400 operators are also 777-300ER operators, that is a moot point.
Part of the reason why the 747-8I and A380 have sold so poorly is the shift to more longer range twins (777, 787, A350XWB).
Even prior to the A380, with 77W deliveries, there wer ebarely double-digit orders for 747-400 conversions anyway - considering the 777F has far better economics than a converted 747-400, its a no brainer in todays world.