I would expect someone who purchased the 135mm expecting a longer lens, to then find out it would be years before they got one... The lack of individual sales impacts the ability for rental houses to rent the 1.7x. As to new lens, I don't understand the push for a UWA zoom. They'd sell a lot more 80-160, 100-200 or a longer prime - the 400mm would be amazing!
As much as I want to see a H7D happen, I can't see it working out. Doing a new back, updated HC lenses, and some sort of commitment to keep the platform going. That won't happen, and let's be honest, the IQ4 will take the next Sony chip without much work, and the BR lenses are up for it.
I think spending the time & money on a 907x II with the 100mp chip. The digital back style would be better as it can be as large/deep as needed to fit the heat. Do a dual pivoting screen like the GFX100. Would be amazing to do a native HC -> XC tilt/shift adapter, without the 1.5x factor & autofocus.