Panasonic digital rangefinder

A debate has raged at DPReview over how much this is like a Leica M. Given my great pessimism about there ever being a digital camera with true rangefinder focusing or any digital non-SLR with interchangeable lenses, this at least offers a few of the virtues of a rangefinder when compared to other digital cameras:

a) traditional control wheels on the lens barrel for focus, zoom and aperture setting, and even a traditional speed setting knob on top
considerably smaller size than a DSLR, which is the only other option for getting (a).
c) A Leica lens; the debate now starts over whether it is a real Leica lens or one made under that name by Minolta (I have heard tha Minolta was also the maker of at least one Leica M or R series lens.)

In respect of the future of good digital cameras than are smaller than DSLR's, is there a future for sensor sizes to grow beyond 2/3" format in cameras like this new Panasonic/Leica? It would mainly take the making of a sensor in say 4/3 or "APS" size but with live preview output. I am puzzled why there is a huge factor of four jump in sensor areas between the biggest, most expensive fixed lens digicams and the smallest one with interchangeable lenses; especially since the cheapest of the latter (Canon 300D) costs less than some of the former (Sony 828).