There's two reasons why commercial airliners are conservative with their projections: the first being that "moonshots" like the 787 embarrass them with programme delays and compulsory groundings due to unanticipated faults costing their clients a lot of money, and the second being that more ambitious projects might threaten to render the aircraft they expect to deliver to their existing loyal customers over the next five years prematurely obsolete. (airframe/engine update cycles and percentage efficiency improvements are pretty predictable, and embedded in a lot of financial models that involve big Boeing/Airbus customers borrowing a lot of money)

But to put that in context, the major airframers and engine manufacturers also have a lot of talented aerospace engineers very keen to make their mark with more radical innovations, well-publicised "concept planes" with funky designs like open rotors and even those skunkworks projects likely have a bigger budget than aerospace startups