True in general but I disagree on specifics and magnitude. While those -- and other factors, such as exposure -- are limiting factors, and very important, THE primary limiting factor, for me -- who has used multiple dSLRs, POSes, and Androids- and iPhones-as-cameras -- and I suspect many others, has been one thing: time-to-capture.
The time it takes between me pressing the shutter button until the camera records the shot as usable data -- this is the important factor. This is what is holding phones back. On phones, I have to wait sometimes up to 0.25-0.5 seconds or even infuriatingly more between the time when I tap the software "capture" reticle and it records the image. This is what is unacceptable in modern phone cameras. By that time the cat has moved, the play is over, my hand has shaken.
On dSLRs this is refreshingly fast. I half-press to focus, complete-press and now I have the image, nearly instantly from a human perception of time, even given the mechanical slowness of the mirror movement. I know the limiting factor is for all practical purposes my own reflexes. For the phone, I know it's crap hardware/software.
On the flipside, the phone is what you always have with you, in a given moment, and reaching for a device in your pocket is much faster than going back to the car to dig through your camera bag for your massive SLR. I say this as someone who has used and loved SLRs since the film days. I'd love to see the time to capture on the phone approach that satisfying threshold you mention on SLRs, because they already help me capture so many moments I'd otherwise miss.
_Those_ cameras are doomed because the iPhone does what they do, in many cases the iPhone does it better, and the iPhone is cheaper and smaller. At least an interchangeable lens camera will always have the feature that you can put a different lens on it. On the other hand people do make optics for the iPhone, too, so it's certainly not impossible for an "interchangeable lens iPhone" to exist in some way at some point.
I dunno, my non-interchangeable-lens camera (Canon SX40) has a whole range of features which are important to me and that the iPhone doesn't (and will never) have:
* 30x optical zoom
* optical image stabilization
* tripod mount
* flash hot shoe
* 58mm filter mount
* good ergonomics & no touchscreen
* RAW files
* scriptability of shooting e.g. for thunderstorms (camera triggered by lightning)
As an advanced amateur photographer (http://photos.aballs.com/), the iphone getting better and better and better has tremendous appeal. My photos are instantly geotagged, and I can immediately upload them to twitters, IG, and share them directly with people via WhatsApp and SMS.
Every year I get a new camera (along with new features) from Apple for the cost of $200-300 (New Contract Free Price - Selling my old phone used). That is nearly impossible to do with my SLRs.
For serious travel photography, I enjoy using my 5D2, but there really is no comparison between using my full kit, and using my iphone.
The time it takes between me pressing the shutter button until the camera records the shot as usable data -- this is the important factor. This is what is holding phones back. On phones, I have to wait sometimes up to 0.25-0.5 seconds or even infuriatingly more between the time when I tap the software "capture" reticle and it records the image. This is what is unacceptable in modern phone cameras. By that time the cat has moved, the play is over, my hand has shaken.
On dSLRs this is refreshingly fast. I half-press to focus, complete-press and now I have the image, nearly instantly from a human perception of time, even given the mechanical slowness of the mirror movement. I know the limiting factor is for all practical purposes my own reflexes. For the phone, I know it's crap hardware/software.