I've never had an iPhone but I do use the wife's iPad, and it's too slow for sports and too noisy for indoor/low light situations. My cell phone is about as dumb as can be -- no data, no internet, no text; just use it as a phone. Am I in the minority? Absolutely.
P&S sales will continue to go down until the smart phones saturate the market, but they'll still sell in the hundreds of thousands/millions. The problem with cell phones is that they are size limited. They are expected to fit in pockets (at least for guys), and they still need to provide all the other functions expected of them. P&Ss can be larger, and can use better lenses, larger sensors to their advantage. Perhaps whatever replaced the CMOS sensors will be able to make smaller sensors as good as FF today, but until those disruptive technologies arrive, we're stuck with incremental improvement.
A lot of friends use the phone as the primary camera already, but the quality of the pictures taken are not very good and they don't back up the data. So, what happens if the phone is lost/damaged/stolen? They get a new one, but they've lost everything. There goes a few years of pictures. Maybe they can get some reduced sized versions from Facebook or whichever app they use, but those often aren't high enough resolution to print. And when those companies go out of business or change their model, there is no guarantee that those images would be preserved.
Photography is a mostly a hobby for me, and I do it to preserve memories. I might have a dozen pics of my grandparents, and a few dozen of my parents before they got married, and a few hundred of them since then. Now that I've had kids, I've snapped thousands of pictures. We take the best ones to create digital scrapbooks (easier to duplicate if the kids want their own copies later), and then print them. My kids are young, but they've already forgotten a lot and they get a kick from looking at the scrapbooks, which jog our memories and get the conversations going. Those conversations don't happen looking at an iPad. Quite a few friends have remarked how they wished they had scrapbooks/photo calendars like that, but they don't have the pictures to make it worthwhile. When film was king, everyone developed their rolls and got prints. Those prints usually were stored in shoeboxes in closets, under the bed, etc. but people still had them. What will people have to show the next generation?