But as sales have shown the 788 has captures a huge market and the -9 is selling out its slots aswell . Airbus have sized the 350 very well given that boeing allready had a successfull product with over 500 sales by the time airbus launched (or rather re-launched) . The A350 and 787 arent much different in Fues. width despite the XWB affix (this is nothing like a 330 , 777 difference) . The only thing that is different is the wing , the 350 wing is very well built for high capacity and around the -1000 , probably the sweet spot for the 350 wing is between -900 and 1000 varients (you would probably know better then me) , whereas the sweet spot for the 787 is much lower (in capacity/size) ie in between the 788 and 789 . Boeing can probably do a strech to a 787-10 but would most likely have to sacrifice on range/payload (with their standard 20% strech) . I beleive that if boeing is willing to spend 2-3 billion$ in developing a new wing , undercarriage for the 787 more optimized for HGW then they can compete well with the 350-900 and 350-1000 , given that the 350 is only about 5 inches (?) or so wider then the 787 IIRC .

What say you?

I say: well put!
Boeing aims foremost on its present customers of the B767 and those who have procured the A330-200 and -300, which Boeing acknoledges have sold well. It was in my opinion never intended to replace the B777-200, but the -10 would do so. Stretching it further would compromise the original plan.

Like always the airframers are making each others business difficult. The B787 caused Airbus to more or less replace the A330 earlier than planned. The A350 will cause Boeing to replace the B777 earlier than planned. Replacing the B777 is indeed difficult, as benefits would be low, I think ~10%.