The problem with the "alleviating congestion" story is that nearly every airport has far more short-haul flights than long-haul, and far more flights on sub-200 seat airplanes than supra-200 seat airplanes. Therefore, the A380's ability to alleviate congestion is very limited. It is just not economic to operate on short sectors -- and most long-sector routes (aside from NYC-LON and a few others) don't support multiple dozen daily frequencies that would be a prerequisite for the A380 to be both economic and to make any dent in congestion. Consolidating 3x773s into 2xA380s on a route isn't going to move the congestion needle.