I think that Lankana might be a smidgen off the mark with four engines though - why re-invent the A340-600? Come to think of it, why invent the A346 in the first place?!
And what was 777-200 in the first place, other than A330-300 reinvented?
Bit unfair Lucifer - I suspect that Boeing have in mind just such a response to the A350-1000: another stretch of the fuselage and push the GE90s to 125k/lb (I think that's the max for engine out controllability?).
But stretching the fuselage also stretches the leverage for fin.
Actually, 4 engines does include an outboard engine - which has long leverage for asymmetric thrust. Wasn´t Boeing 777 originally intended to be a trijet? Trijet does not have any outboard engines, while the wing engines have less thrust each than the engines of a twin would have... so better for engine-out controllability.