Airbus is exploring the potential room for structural growth of the A350-1000 but insists this is not indicative of plans to develop a further stretch.
A350 programme manager Didier Evrard says the airframer has looked at limitations for increasing the size of the A350, and the nature of any structural restrictions.
He says there is a "lot of potential" in assemblies such as the landing-gear - which will have a six-wheel bogie on the -1000 - but adds that it is "far too early" to talk about a fourth member of the family.
Airbus head of product marketing Sophie Pendaries, during a briefing in Toulouse, says: "When you've a strong production line it would be stupid not to study."
But she says the airframer has yet to see a "major market" for a larger aircraft, adding: "We have an A350 family which is quite strong today."
Evrard says Airbus expects to start cutting for sections of the -1000 in mid-2014 although specific initial parts are likely to be crafted earlier for the pylon, to aid engine development work.
"It's becoming extremely high in my daily managerial attention because we are now entering the industrial phase of the -1000," he says.
"We're no longer talking about design. We're dropping data to the tooling manufacturers."
Airbus is also set to expand its final assembly line at Toulouse, initial details about which Flightglobal revealed last June, to provide additional capacity for -1000 production.
"The -1000 will have to insert itself into a manufacturing flow that will be going at very high speed," says Evrard.
Airbus intends to create a third Station 50 fuselage assembly point, dedicated to the -1000, in 2015. Once production is stabilised it will use this station for the -900 as well.
Expansion at Toulouse will also provide four Station 40 wing-join points as well as a fifth Station 30 test area.