Supposedly, Airbus was aiming the A340-600 as a 747-400 alternative. Only one problem: the 744 seats quite a bit more passengers than the A340-600.
Now, the A346 as a 747 "Classic" replacement, that's a very different story.
By the way, according to Flight International magazine, Airbus plans to have increased gross weight versions of the A346, which could mean that the A346 could have essentially the same range as the A340-500 but with the carrying capacity of the A346. That improved A346 could become VERY viable for a lot of airlines around the world that needs a long-range plane but will not buy the 747.