The 747X program is designed, apparently, to compete with the A3XX. The 747X models are, 747-400X, 747-X, and 747-400X Stretch. In service they will probably be the 747-400ER, 747-500, and 747-600.
The 747-500 has more range than an A3XX, but neither the -500 or -600 get close in terms of capacity OR comfort. The 747-400X itself is just a 747-400 with updated technology and vastly improved fuel efficiency over the 11 year old jumbo. It would also feauture a 777's interior styling. As said, however, the 747Xs aren't quite as big as the A3XX, so they will appeal to a slightly smaller market - this is good for United Airlines and other US airlines which are wary of ordering the mammoth A3XX which seems mostly useful in Asian areas.