The previous A350 used conventional materials. The new A350 PITS (Pie In The Sky) uses composite materials for the fuselage and, perhaps, the wing. Airbus is attempting to push the state of the art to places it has never been before. We have seen how well that works out with the A380 fiasco.
If anybody thinks this thing is going to be developed for 10 Billion Euros, they're dreaming. It will be triple that before Airbus solves all the problems.
They should stick to tried and true technologies. They are coining loot with the A320. Why not just dominate that market?
I just had my first flight on an A320 and I was pleasantly surprised. It was much quieter and smoother than any 737 or 757 that I've ever been on.
However, as you said, Airbus rakes in the dough with the A320, and that aircraft will be slayed by a plastic 737 as Boeing's next project. Airbus won't be able to respond with a plastic A320 until the entire run of plastic 737s is sold out.
By deciding to go with the A350XWB instead of directly to a plastic A320, Airbus has chosen to play catchup with Boeing for the next two decades.
(BTW, Ping to Paleo for his pinglist)