The MF segment is so small, that even if it would increase ten-fold it would still be tiny, so I think it may not follow the exact same logic as higher volume markets. It's a niche market and will stay that way. But as a niche market I don't think it needs to stay as static as it is today.
The "forgotten" customer segment I'm thinking about is the 40-60 year-old amateur that would buy a motorcycle or a small sailing boat or other fairly expensive unnecessary item for a hobby you love and spend a lot of time with. Not necessarily overly rich, just middle class people that has saved up some money over the years and want to do something fun with them. Photography has a solid place as such a hobby, and then it's generally not studio photography but things like birding (135 space for sure), travel and landscape. Landscape is huge among amateurs.
When it comes to landscape tech cameras has a very appealing advantage from that it offers a totally different experience from shooting 135. It has a similar appeal as shooting 4x5" large format (which some still do), you can frame with movements just like Ansel Adams, but you don't need to carry as heavy gear or mess with film. And there exists quite economical solutions too, a Silvestri tech cam with Schneider Digitar lenses can be had new to a reasonable price; but then you need to smack a back to it which costs a lot more than the rest of the system, or you need to buy some "entry level" back which still cost a little more than the rest and leaves you with a poorly balanced system with stitching on the wide side and/or possibly the requirement to get much more expensive retrofocus lenses.
This segment has a pretty large growth potential if backs would be less expensive and more focused to work with these systems. But it's the tech camera makers that could have interest in that, rather than players like Phase One. I suspect that tech camera is kind of stuck in their thinking too though, they're doing okay to well by selling in small numbers and are not hungry enough to want to grow their business.
The trend in tech cameras seem to be to make them more similar to an overgrown mirrorless A7r-like camera, both concerning lenses and camera design.This is to some extent a result of digital back development that follow the needs of the MF SLRs rather than tech cam systems. I think this will reduce the appeal to this amateur segment, then it just becomes a luxury product not a different shooting experience. I'll probably leave MF myself when/if the view camera finally dies, on the other hand it could get a new revival with the appropriate CMOS sensors and backs.
Pentax is just a big DSLR, and I think that works because the price difference is not too large, ie it's bigger and better and priced in a reasonable way. But it appeals to a different set of users than a tech cam does.