Well,
Airbus would certainly start to use some billions in development of a new airplane if it is a driect replacement for the A300/310 B767-200/300.
It is no problem to find an economic short to long range 250+ seater, but if your market only sustains a consistent pax load of some 180 to 220 people then you either still fly on 15 to 20 year old airplanes or you hope for a market growth.
And if you build the airplane to be felixible enough to sustain both European/Japanese short hauls as well as long hauls going up to 270 paxes in the 'almost freight' config for the european charter operators, then you face a market of some 750 to 1000 aircraft over the next couple of years...