Quite a bit of uninformed rubbish being offered as the truth here, which I shall attempt to rectify.
The suggestions that the future of the 747 has any relevance or connection to US domestic traffic or US based carriers, points to a total lack of knowledge of the world aviation scene. US carriers haven't ordered a 747 sized aircraft in decades, and only AA have even bothered to get the next biggest thing (77W). Nobody predicts any passenger VLA market with US carriers, least of all the people who produce the things. It may be worth having a look at the Boeing and Airbus projections; North America will soon seize to be the biggest aviation market - China will take that place. It is also not in the US the two big manufacturers are seeing the growth, far from it. It's in the Middle East, Asia-Pacific, Europe and then the US.
Some people have also been taking for granted the marketing gossip emanating from an aircraft manufacturer, namely that a B747-8i will burn less fuel per seat than an A380. But that is only true if you use the Boeing standard seating for the 747 and the Airbus standard seating for the A380. Since those two standards are not the same, it's comparing apples to oranges. The truth is, as should be expected given the generational gaps between the products, is that an A380 will burn less fuel per seat than a 747-8i with an equivalent seating standard.
As for the future of the 747, the order book speaks its own clear language. There are less than 60 unfulfilled orders, 45 or so are freighters. Boeing are currently building white tailed freighters and flying them directly to the desert, and has reduced output twice recently and are now down to 1,75 aircraft per month. There are no signs of any major new order, their best hope is probably that Air China or Korean Air might order 10 more in total between them. Then the curtain will fall over the production of passenger airline 747s, but they will continue to grace the skies for many decades to come.
Finally, the A380 is not in competition with the 747-8 over a possible Air Force One order. Mainly because no such tender has been issued, secondly because Airbus have already made it clear they have no intention of entering such a competition, for all of the obvious reasons. Though I suppose it would be fun checking in on Fox News if Obama ordered a 'French' jet.