>>Which airlines are you refering to? <<

BA specifically.

>>How do you know which airlines will have longer legroom and they will fly full?<<

The A380 seat arrangement means wider seats than the 747 in economy class, and the fact that it has 50% more space and 33% more weight capacity than the 747. This leads to the inescapable conclusion based on the basic laws of maths and physics that the A380 will have more space per passenger even in high density "cattle truck" configuration with 840 passengers than the 747 with similar configuration.

>>If they have longer legroom, why would they want to cut fares?
Why do you think the 747 will be parked in the tarmac?<<

They may not need to. However, people have being putting out statements in this thread (without any basis on fact that I can see) that A380s will be running half full and so won't make good on the big operational per seat cost advantage that it will have over all other airliners (including the 787) because of this. All I saying is that because there is big cost saving to allow price cuts on the A380, if there is overcapacity, a small cut in the fare will fill the A380, and it is the 747 with it's higher operating costs and not the A380 that is going to be flying half empty or sitting on the tarmac. It doesn't mean that there will be enough passengers on all routes, all airports, or all types of carrier for the A380 of course, I am talking specifically about Heathrow which is a slot restricted airport and BA which is a high density route operator with Heathrow as a base. Many other international hubs and airlines will be in a similar position however.

>>I don't understand what you meant by low and high ends.<<

I mean the 747 is being attacked at the high passenger capacity configurations by the A380 and the low passenger capacity configurations by the 777 and A340.