Ok the 737/A320, it goes up and down, mostly short legs. Boeing does not care.The only major cost savings would be in the engines. Just how clean can an aircraft get?
And weight of course, assuming composites will make the difference. There are potentially big economies to be made with an all new airframe.
The NEO is just a stop gap. Its only bolting on a new engine and a few other systems. Its not a major undertaking at all.
But Airbus is on the back foot slightly because they still have the A350 gumming up the works until at least 2013 and with the Neo due 2015 it will put them behind if (big if!) Boeing can deliver.
I'm wondering if Neo is a bad idea.