If GM releases a larger gas engine it had better walk all over the 7.3L Godzilla considering the only advantage Ford has is the option to pair a lower rearend behind their gas motor than GM does.  Power wise the torque and hp curvers between 7.3L Godzilla and the L8T are almost identical (within 2.5%) so there is little to no point in making a bigger gas that makes the same power.