4 engine planes are dead. Period.
The A380 is a total failure and a complete albatross: Without Emirates, frankly, Airbus/Eads may not have survived as a company.
The 747 can add capacity, as you suggest, yet...
Did you mean the A350?
The A340 is out of production.
As the 787-8 and the A380 are penalized with having 4 engines, drastically limiting their sales, apparently there is not a way to reduce the power on (2) engines during flight to conserve fuel....
With the -800 dead and now this cancellation for a number of the -1000's, things are getting a bit dicey for Airbus' A350 other than the -900.
It appears Boeing has the 350 bracketed with...