I might rejig the sentence to say the A380 is not selling as well as expected and, freighters apart, the 747-8 has almost no appeal for the airlines. It is a tad ironic that, in what will be its final iteration, the 747 has pretty much reverted to the role for which Boeing designed its first wide body and, having lost out to the C-5, was supposedly destined for the cargo role in civilian service after a short life as a passenger hauler until the expected adoption of SSTs by the world's major airlines.
Manufacturers may propose but the airlines make the decisions.