|Quoting Prebennorholm (Reply 49):|
And one more thing: Even if the 387 will carry a lot less payload for increased range, then it may not end up with equally reduced floor space. That way it may introduce a new level of comfort at affordable prices. We will see.
The A380 is already a very heavy aircraft for the amount of payload it carries, which somewhat offsets its advantage over the 747-400 in terms of aerodynamics, engine efficiency, and advanced materials. Part of this stems from its double-decker structure, part from the oversizing of the wing and other structures in anticipation of an eventual stretch.
History has not been kind to shrinks; only the A330-200 has really been successful. This is because stretches tend to reduce the OEW per seat or pound of payload while shrinks tend to increase it, since there's a limit to how much weight you can tear out of an existing structure. An A380-700 with equivalent range to the 747ADV would probably be at least 100,000 lbs. heavier. With 787 engines, the 747ADV would match or beat the A387's specific fuel consumption, and aerodynamic and structural improvements would further close the gap.
It's possible that Airbus could use an A387 with A388 fuel capacity for ultra-long haul flights that need more payload capability than the 772LR or A345 can provide. Like the 747SP or rumored 772ULR, this might be a niche good for a few dozen sales. However, on sub-8,000 nm routes where the 747ADV is a viable option, it's hard to see how the A387 could be competitive with such a weight disadvantage.