A lot of discussion about what we want in a digital RF includes, fairly consistently, the "are there enough RF photographers to support the market for such a camera" question. Also fairly consistently the views on this seem to be slightly to decidedly negative, with some exceptions of course.
I for one think it might be helpful to simply think in terms of photography and photographers, not RF photography and photography. Photographers, whether amateur or pro, are a very practical and adaptable lot. The market responds to new ideas and implementations. Just look at the growth of RFF. I cannot believe that this is anything more than people discovering or rediscovering a tool, a mode of photography that meets a need.
Also look at the very invention of 35mm photography. "Too much compromise" in such a small format many felt. And yet the very invention of the Leica provided the foundation for an entirely new sector.
So I believe in the "if you build it they will come" school of product development. What I have learned about marketing is that most marketing people generally miss major trends if they are left to actually think up a new product. It is usually the inventors, the technically creative types who succeed at a breakthrough product. It is the true amateurs, i.e. the lovers of a craft, who have the vision and fortitude to create the future.
So given the current technical hurdles with a digital RF, (which seems to be tied to the flange to film distance) I think we are only in the very initial stage of product development and definition. I applaud both Epson and Leica for their efforts. I really think someone else will come along and contribute to the effort, perhaps with the "breakthrough" product that will carve out a new market segment. I have no clue as to whether any of the "big boys", (Canon, Nikon, Sony, etc.) will be a player, though conventional wisdom would say not. Whoever else might play is open to lots of guessing, and I for one think a big surprise would be fun.
Why I think there IS a potential market is that outside of sports and a few other specialized uses, most people use a fairly narrow set of focal lengths. These focal lengths (moderate wide angle to short telephoto) are the sweet spot of RF photography. All it takes is for one person, one small team to dream and design.