May I ask how B737NG can be successful as it is only a variant of B737Classics? The answer is very simple... Boeing designed a new wing with better aerodynamics for B737NG and now Airbus will do exactly same with A350 when upgrading it from the A330.
Yes, however the B7e7 is not just a new more efficient design. The 7e7 is built with very different materials much lighter than the current in use.
I'm not convinced that B7E7 will be as light as Boeing claims.
It might, it might not. But it will be significantly lighter than the A350.
However, I'm quite sure that Boeing is able to solve most of those problems but definitely they must do some compromises with the design as well and these compromises have always negative impact for the performance.
Boeing isn't doing all of the work, they have many contractors (apparently more than they ever had) in this project. So they are not doing all the R&D.
B7E7 is only ink on the paper so before the first prototype is build you should be very sceptic when talking about performance or weight. Same thing applies for A350 as well... Some people seem to believe everything what the PR divisions of aircraft manufacturers say just like they were some gods.
You are right, however, an 'old' ('330NG stretch' plus a few things) concept cannot compete effectively with a brand new concept.
Judging by the original link from the thread, Airbus seems to be going after the 777 instead of the 7E7, probably because they realized that the 350 will not be up to the job taking on the 7e7.
New aerodynamics help a lot, but that's not the entire picture in this case.
: Formula 1 cars are built out of carbon composite, you cannot win a F1 race with an aluminium car. BTW, you could go a lot further (or save gas) with a carbon composite car then you would in a standard metal car.