What would the FFF have to do in order to be competative?

First of all, I have a great deal of respect for Kazuto Yamaki, CEO of Sigma. His passion for image quality and affordable high performance lenses is in my opinion unmatched in the industry. Which is why I am looking forward to seeing the release of his FF Foveon camera. 5 years ago I invested in an SD Quattro and a few Sigma mount lenses to see what kind of images the Foveon technology could produce. I didn't mind the ... unique ... ergonomics, the slow frame rate, or working with the Photo Pro software. I generally use a tripod and take my time with image composition and processing. I spent about a year gathering images but in the end regretfully sold the kit and moved on, first to the Nikon D500 and then to my current Panasonic S1R.

Why? In two words - color accuracy, especially with anything in the composition that required rendering a gray tone. Two sample images, both rendered from a Quattro .DNG:

Simple shots, which shouldn't be a problem, given that the light was more than adequate. Here are the crops of the shingles on the shed and gravel on the path:

Both show a completely unacceptable level of green and purple false colors.

I've read the extended discussions of how people on this forum think the sensor and image processing has been improved since the Quattro.

I sincerely hope so.  If the new FF can give me clean colors on all subjects in both normal and challenging lighting situations, I will certainly be considering it as a second body to my S1R.