Maybe the title sounds like an essay. Quite not so. It's a question.
Look at the flagships of the past. Qualia 010, SR-007 Mark II, R10, HE90...
With headphone technology that we have now, what can still be improved upon? Lighter, stiffer diaphragms? Magnets with denser magnetic flux? More delicate cavity design? An entirely new driver technology?
Just a question and some discussion. Have fun!