Airbus A380 is its largest jetliner on offer, with 2 widebody decks along the whole length of the aircraft. It has 10-abreast economy lower deck & 8-abreast economy upper deck, and very curved upper deck design like that of 747 upper deck.

Because of its huge size, Airbus has to completely redesign the aircraft, rather than deriving from A340.

But I don't think the design is good.

First of all, this makes very high development cost, and higher maintenance cost for airlines.

Secondly the 10-abreast economy lower deck makes passengers more difficult to get out of seat & go to the aisle, and more difficult to serve passengers meals & drinks. This is not good compared to 8-abreast economy layout of Airbus A340, where no passengers are more than 2 seats from aisle.

Lastly the upper deck sidewalls are so curved that only drop down bins can be installed over the side seat blocks, thus making serious nusance to passengers below, and much more dangerous. Ironically all other Airbus aircrafts features no drop down bins design!!

So it is much better for Airbus to develop a large jetliner which is based on A340 cross section, with 7-abreast twin aisle upper deck section built across most length of the aircraft. This not only ensures more comfort for passengers, but also reduces developement cost & maintenance cost for airlines.