Interesting debate...
I personally think the A380 will be a success. You just have to look at the big two long haul airlines in the UK; BA and Virgin. Moving into fleet renewal for their 747's they have both ordered A380's. There are a lot of 747-400's flying around in the world and surely the A380 will be first choice for their replacement. I accept that the large body twins are a much better proposition these days but you still need an aircraft for high density routes that can accomodate a significant number of multi-class passengers.. On that score the A380 is alone.
Virgin can fill 4 747's a day to MCO alone. Don't see the 787 replacing this...
RP