Phototone,
I don't disagree with some of your musings, but your conclusion may be overly optimistic.
I don't think they use the same lines to coat, PE might know for sure. The R&D spill over is nice. That's the "mostly". If a still film reaches less than a certain economy they will dump it, (as they have already demonstrated with specific emulsions) while still producing the MP stocks. On the last film I shot we used over 120,000 feet of 35mm. That kind of usage on a broad scale keeps the wheels turning for motion picture stock, but as I said, I'm pretty sure the actual production is unrelated. I would like for you to be right.
There is the common misconception that the films are the same, and that MP film sales will somehow keep still film in production. This has already been demonstrated to be false. By in large only sales of a specific emulsion keep that emulsion in production.
Also, Ilford (Harman) currently produces only black and white emulsions, and has a fundamentally different product line, market position, structure, scale, and outlook.