M43 success proves the public want small cameras with truly good image quality.
However, so far none of the companies involved in M43 has come with a camera without serious compromises. Every model lacks always an important feature.
Also, looking at sample comparisons between 4/3 and APS, the second always wins by a notch and dusting the first one at high ISO's. Good high ISO performance in this type of camera is very important because they are often used under low light circumstances given the reason of their existence.
Since M43's downsizing is limited by the size of the lens, it's physically impossible to produce a pocketable interchangeable lens model, leaving M43 technology as optimal for light non-intimidating easy to carry cameras but certainly not for the pocket.
According to my empirical calculations, a mirror-less version of the APS technology would yield an interchangeable lens system very close in bulk, weight and stealth to M43 but with the huge advantages of a sensor double the size.
Best
Eduardo
