Cars are also limited by the need to have seats and controls, and somewhere for the engine. A new sportscar still fits the same sort of form factor as a Morgan, but it's utterly different.

The reason for Brompton to start again and reinvent is because they, themselves have proven that a new design can suddenly dominate the market. They did it, and eventually, someone else will do it. If Brompton wait for that to happen, most of their market will be gone. As far as evolution, Brompton ARE doing it, but MUCH too slowly, and with no real innovation. Folding bikes are driven by innovative new features which work well despite/in combination with folding. What have Brompton done for us lately in that respect? The can't even get a decent multi speed transmission together.

At the moment, other manufacturers are gradually catching Brompton up. Soon, someone will be making a Bromptonalike (Dahon have a similar fold on the way, Merc is already out there). At that point, Brompton will be trading on quality alone. They COULD be trading on quality, and on some other improvements (a better luggage system, a working set of folding bars, effective, reliable folding pedals all spring to mind) which are as well designed from the ground up as their bike is, but they aren't.

Then, eventually, another revolution will come. Someone will think of a way to build a folder that either folds just as small and easily and Brompton and rides better, or folds even smaller. When that happens, what will be left for Brompton? Organisations should always aim to change and take the next step BEFORE the pain strikes.