Say Again Slowly wrote:
“I really believe that with a few years of 'normality' we may get back to different desires about a/c than purely cost driven solutions.”
I'm not sure how you can separate "desires" and "cost" when you talk about large aircraft development. Sure, your desire can be based on non-profit things like aesthetics or innovation, but you will still have to spend the big bucks to build the thing. Unless you pay for it all out of your left-over cash, you will have to have a method of recouping the development costs. Since all airlines today use basically the same methods of financing, the airliner manufacturers tend to all come up with basically the same solutions. Ones that (we hope) will let the airlines and the manufacturers make enough money to pay off the bank.
There is an interesting new trend, however. We are seeing a very small number of ultra-rich individuals who can spend the big bucks, for totally “non-profit-making”, personal reasons. For example, look at space tourists, the people building replica antique aircraft and cars, and the people lining up to ride the x-plane contestants. Maybe, someday, one of these big spenders will build revolutionary airliners (or electric cars, or whatever your pet project is). And maybe, just maybe, some of these pet projects will turn out to be practical in ways nobody expected.
In the mean time, committees of bankers and accountants will force the committees of engineers to turn out similar products. However, I have to totally disagree with the premise that this means there is no advancement. Instead, it means we all advance at roughly the same rate, and in roughly the same directions. If one day some radical spender actually proves swing wings (or whatever) are better at making money, all new airliners will very quickly adopt the new technology.