There are some advantages to sending 2 777s instead of one A380 on a route - the airline can offer 2 different departure times, and pax like choice, and having 2 departures is useful in the hub systems that the airlines are now organized around. Also, the issue of route fragmentation; ie, instead of one A380 flying SFO to Tokyo, it may be better to have a 777 from SFO and another 777 from San Jose (just an example). The A380 will be amazing, the only issue is which routes will support such a big aircraft under the current way airlines are organized. Of course, BA could fill the A380 between JFK and LHR, but I do not see BA going from 6 flights per day to 3 per day on that route.
If the horrors of 11 Sept have a long term impact on the flying public, the need for the A380 may be reduced or delayed. Airbus is looking at this now but, of course,its too soon to tell.