Pretty good point but of course it all comes down to numbers. Economics of scale and all of that. Im a DSLR guy myself. DSLR for Video and stills and have a BMCC as well for video only. How large a market will FF have in 3-5 years and will it be large enough to merit continued investment? I like your point and Im thinking that we might see a much smaller product line down the road if the demand shrinks more.
I worked for Apple for 15 years and I'm well aware of what technology can do and how focused companies like Apple are. Apple with a market cap 10x that of Canon and Nikon put together has no intention to pull back on developing what small mobile products can do. Of course a smart phone is not a FF camera "Duh" ... but its all about market economics pure and simple.
Personally my view is that Canon have probably taken the right decision in trying to target video more with there very high end professional releases. For the amateur market I suspect that phones are "good enough" for more people than they are with stills simply because your looking at lower resolution output.
To me its looked like Canons tactics in recent years have generally been to target the high end markets with quality and the low end markets with price whilst tending to focus less attension on the middle. Honestly I cans ee the logic behind that too I think the "gadget" market is a very tough one to go after, you have consumers with limited amounts of money to spend who also demand constant advances.