well i'm a newbie around here and i can tell you the dRF market is certainly growing.
photographers who grew up in the digital age and all they know are DSLRs are slowly gravitating towards dRF. perhaps not as their 1st and main body but definitely as a creative choice.
a main stopping point for them in picking up a RF is that it is film in nature and they have grown accustomed to both using digital and the efficient workflow process around digital.
perhaps zeiss/sony recognizes this growing market and feel it is time to produce a new entrant. after all, if cosina/epson has done it before, it is not exactly rocket science to come up with one. again, for this market for 1st time rangefinder users, full frame is not a major consideration.
one thing people tend to overlook is that sony has proven in the past and is still willing to push products at a loss or almost at a loss for market share.
2nd hand M8s can be viewed as both a problem and opportunity. lower prices means lower entry barriers for people wanting to pick up a dRF. but that also means the market for dRF increases quite quickly. if sony/zeiss can have an offering priced perhaps 10-20% premium on top of current 2nd hand M8s, maintain 1.3x FOVCF, and yet able to achieve better noise control, you would see a real market for them.
i agree that sony has to be the main driver for such an effort. zeiss seems to be content as an optics company.