Interesting post, chornedsnorkack - thanks.
I would suggest thought that whilst there may well be some blurring of the competition between the 380 and the 787, fundamentally they will live and die on how well they serve the markets they are designed for. I would agree with you, it is likely that we'll see 787 on hub-to-hub routes, ones that cannot support a larger aircraft; but the real target of the thing is going to be longer, thinner routes, and if it can't win in that market, it is dead.
380 will, I think, pretty much always be a hub-to-hub beast. I can't really see one on, say, Manchester-New York anytime soon.
Just a thought - I would say that the 757 was killed off less by the widebodies, and more by the fact that Boeing in their wisdom grew the 737 into its market space... why buy a 757 when a 737-800 can do the same sort of job, and means you can keep your fleet simpler?