For the digital "M" to be successful for Leica, the rangefinders natural advantages must be exploited. Small size, ease of use,quality of output and leica's legendary quality and optics, must all come together in one package. The rumored "M" meets most of these criteria with an adaquate 10meg file size, and even the 1.3 crop sensor is close enough to a full frame to use the existing lenses (with the addition of a wide, wide angle-21mm equivalant).
However, the only way that the expected 3K + cost for the body only would be justified for me is if the mechanical "camera" part was a upgradable by purchasing new backs as the digital component becomes obsolete. I know this is what the intent was for the digital back for the SLR, but the interface was, by necessity, way too complex.
Imagine a digital M body module that you could buy without worrying about obsolescense or incompatibility issues within a matter of months. Design the body to interface with any technological digital or electronic advances thru a simple pin contact system like SLR lenses do now. Your body would be future proofed!
In this senerio, paying 3k or more for a quality body that could become a legacy object for the photographer/collector would not seem so strange. And for the true user, new backs with extended dynamic range, lower noise and greater resolution would always be available (or at least possible!)
Only the simplisity of the rangefinder makes this practical. A current "M" body with added communication contacts for the back would do the trick. Forget auto focus or any other nice features for now..... maybe for a later body but some would keep their MF anyway. The idea is a simple body that does what a rangefinder is supposed to do, that is beautiful, that is desirable, that is lusted after, and will produce the best digital images that the current technology can produce.