I think it's fair to say that the 787 will never supercede the 747. imho the 747-400 still remains the de facto target to beat in terms of premium travel. In time, I'm sure that the A380 will prevail, but the 777 never will, due to the cabin/galley/toilet layout and the noise levels.
Just ask your prem pax which they prefer to fly on, the 744 rules over the 777.