A few years back, when the digital film debate was quite uncivil, and the digital people were proudly posting numbers of digital cameras vs. film cameras as conclusive evidence that film cameras were going to decline to zero, I reminded them that cell phone cameras would soon be more numerous than digital SLRs and with the same logic they would soon disappear.
It is sort of like extending graphs that appear linear, sometimes, they are only linear for a period.
Fine photography and cameras have always been a niche. Same for B&W, 15 years ago, Photo tech people told me it was far less than 1% of sales.
Extrapolation is difficult, and to some degree pointless. I know people still shooting glass plates.
That said, it is reasonable to assume that quality of camera phones will increase, which is not to say that it is unlimited.
What we accept as "good enough" is up to "us", perhaps in a Pogo sense.
Regards, John