I think the big blow to Airbus was Boeing's monster 777-300ER twinjet. What a beast. Damn near a 747-400ER with much better operating costs. It really killed the A340, and will rewrite the dynamics of much of long-range passenger travel.
But the next big battle is the 737/A320 replacement. And Boeing needs to get moving fast on that.
Airbus knows it got wrapped up in its own propaganda with the A380, and was caught flatfooted by Boeing with the 787. So it tosses out an A330 derivative (the A350), and uses political muscle and extreme discounting to sell enough to get a production go-ahead. But it seems clear Airbus does not intend to be caught flatfooted again.
I seriously doubt Boeing would develop such a variant. It would require major changes to the wings and other systems on the 747-8I. The whole point of the 747-8 was that it required little development beyond adapting technologies developed for other Boeing programs like the 777 and 787 to the 747. Making a very long ranged variant would require longer and strengthened wings, heavier landing gear, bigger engines, and a strengthened fuselage to carry the additional weight of more fuel. The engines may become available if Boeing builds a 787-10X stretched version. I doubt there would be much benefit to Boeing in spending the other money necessary to build such a long ranged variant of the 747 when there would be very small demand for it.
The 777-200LR shares much of its development costs with the 777-300ER and 777-200F. Those planes will probably be built in 500+ quantities over 10-20 years. It could even be more if some of the additional air force tankers are based on the 777-200F. The 747-8 freighter and intercontinental models are expected to sell 200-400 airframes over the next 20 years. I don't see how a 10,000nm ranged 747 would sell enough copies to make economic sense. Perhaps an even larger stretch of the passenger version with the same range as the 747-8I could be built using common parts, but I would still think it would not have that big a potential market compared to the development costs.
If the 777-200LR were to operate successfully on the LHR-SYD route for several years, Boeing will probably build a long ranged variant of the Y3 twin-engined replacement for the 777-300ER and 747 which will be built of materials used in the 787 and later projects.