A320 / 737 Successors
Some time before the current speculation, I thought that, despite telling the world that sufficiently "transformational" technology to warrant all-new narrowbodies wouldn't be available until the early 2020s, Airbus and Boeing would have to, at the very least, do a refresh / re-engine well before then - if only because it wouldn't be environmentally acceptable to be seen just sitting on their hands for another 10+ years. Clearly, they would be hugely reluctant to mess with their cash cows - each with thousands of orders outstanding.
Airbus now seem likely to launch a GTF / LEAP X powered upgrade and Boeing were expected to follow suit. However, the talk now is that they might go all-new instead - presumably they have concluded that a re-engined 737 would not be competitive with a re-engined A320. A re-engined, sharkletted A320 would cost approx $2bn to develop and reduce DOCs by 15 - 16% with EIS 2015, whereas an all-new aircraft would cost $6 - $8bn to develop and, Boeing say, reduce DOCs by 15 - 20% with an EIS in 2018. An all new narrowbody with EIS in 2018 would, presumably, have more or less the same technology level as the C Series.
I don't understand how these numbers would stack up for Boeing - to spend so much more to develop a "conventional" aircraft with a relatively small DOC advantage over the re-engined A320 and risk being trumped by a "transformational" (UDF-powered etc) all-new Airbus less than 10 years later -seems risky to me. But, I suppose if they can't make a re-engined 737 competitive with the A320, they don't have a choice. Stuck between a rock and a hard place or am I missing something?