For day to day activities, sure. For professional photographers? No way! What will I do with my huge collection of canon and nikon lenses? Sure, I could spend $250 to get an adapter to put them on my iPhone but WHAT is the point of that? I could sell them all, but then what will I do when I really do need a 300mm telephoto lens for nature, concerts or sports? Perhaps the biggest feature the iPhone is lacking that no accessory exists for is a hot shoe. I use off camera flashes and profoto kits in the studio on a regular basis, and yet, the iPhone doesn't even have the ability to fire my cheap little $30 flash I use with my P&S cameras. What about video? I do a lot of video work and yes, I've used my iPhone as a B camera before, but it is by no means a professional video camera. Here's a list of CRUCIAL features for a professional photographer, or even an advanced amateur, that the iPhone doesn't have:
White balance control
Manual exposure control
Aperture Priority, Shutter Priority
ISO control, high ISOs
RAW files
Interchangeable lenses
AV I/O
Variable video frame rates
Tripod attachment
DOF preview
Hot shoe
etc., etc.
There are apps and accessories that take care of a few of these, but not to the extent that a DSLR does straight out of the box. Why would I spend hundreds on accessories and apps to bring my iPhone up to par with the DSLR I already have that will produce a better image 99/100 times? There is nothing obsolete about DSLRs, and a lot of what your OP touts as the advantages of the iPhone as a camera are present in mirrorless and M4/3 cameras like the Panasonic GH3, which is a far superior camera to the iPhone. And I can't stand electronic viewfinders. I will be keeping my mirror and pentaprism for a long time.
Sure, the iPhone has completely replaced my point and shoot, it is a FANTASTIC camera and I use it every day (I certainly can't say that about my DSLR) but it will not be replacing my 5DmkII any time soon. Camera phones are awesome and have opened up a whole new world of photo sharing, which I love. I love seeing my friends lives in pictures and that having an awesome camera in my pocket 24/7 encourages me to document what I'm doing and whats around me. But camera phones and DSLRs are very very different tools and the iPhone will not be putting Canon or Nikon out of business any time soon.
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This is super important. Optical zoom is essential for any halfway decent point and shoot. The camera is such a central feature of the iPhone, I always wondered why they couldn't put a nice zeiss 5x lens a a small REAL flash right where the apple logo is. Check
this out. It doesn't have the greatest lens in the world, but it sure is small. Why isn't this in the iPhone? Apple is too concerned with thinness and not enough with quality.