Airlines are wary of investing a few billion in the final derivative of an aircraft type. I predict the 747-X will not be built, unless Boeing do it purely to stop ANA and JAL falling into Airbus territory. Other traditional 747 customers / Boeing stalwarts such as Thai will probably go A380 anyway (hey, if Qantas can anyone can). But building the 747X for ANA, JAL and Koreanair will make the 757-300 or the 767-400 or the 767-200NG look like bestselling cash cows by comparison. Who else is gonna buy it? United? Don't bet on it, they love Airbus products and being Airbus' biggest customer, they'll probably get a discount that will make Air France's eyes water.
I predict the 747-X will not be built.
fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz