I don’t think it’s entirely correct to say that it’s difficult to build new airports in the First World; Spain seems to have found it far too easy for example…… The real problem lies with major hubs, particularly in areas that are already highly developed. Let’s call them mega-hubs. I would agree that the A380 is ideally suited to flying between mega-hub pairs, but how many such pairs are there really? Willie Walsh, who I would guess knows more about running an airline than most of us, seems to think that the scope is limited. And the A380 isn’t the only aircraft that airlines can upsize to if they need more capacity.
Ideally suited to flying between mega-hubs pairs that don't need frequency. For example, there are hardly any A380s between LHR and JFK because several daily flights are required for the needs of business pax.