The 773er lacks the legs to carry a useful load longer than 12hr, its payload restricted even on a ADL to DXB! The 77x will improve on this. But Pax will still be loaded like sardines to ensure the seat/mile costs are as advertised. And it is a category F aircraft for takeoff and landing (well anytime the wingtips are not folded). This limits enroute ALTNs. So more ETOPs (or is that LROPs now?)
Don, you know the 300ER is a derivative, and was designed as a 747-200 replacement, the fact is it was so much better than was envisaged it is being used on missions it was never designed to complete. The 380 for all its opulence is a gas guzzler and only truly works when you can get upwards of 80-85% in, with a good % of premium...not upgrades.
The hubris that we all know exists within the largest 380 operator in the world has until now delayed more capacity discipline on routes that don't support the beast.
If ADL ever goes onto the 380, it will most certainly not be payload restricted, it will however lower the margins and most likely reinforce the reality that the 380 is infact a niche airframe with limited appeal.
In my inebriated opinion the 380 in its present form will go the way of the dodo sooner rather than later because its appeal has already passed, glamour and grandeur will again be replaced with pure economics..within reason. The future widebody long haul machines will be predominately twin not 4 engined...even if CASA doesn't agree.