I'll wait to see the reviews but I'm sure the 7+ camera will be more evolution than revolution. Premium phones have been taking good enough photos for at least a couple years now. This will be a continuation of existing trends.
The problems with phone cameras (and small sensor cameras more generally) are (1) hitting the resolution limits of the optics, (2) noise, (3) lack of dynamic range, (4) lack of choices in quality lenses, (4) fixed aperture, which means no creative focus effects, and poor performance in low-light settings, (5) software based (and therefore slow and sometimes inaccurate) manual controls over shutter speed, focus, flash, etc., (and more generally, a much less efficient or adaptable physical user interface than a dedicated camera) (6) often limiting output formats, with lots of in-camera processing wiping out data from the raw image.
Any 6+ megapixel DSLR (e.g. the ones from the early 2000s) with a nice lens easily outclasses the iPhone or any other phone camera, in the hands of a photographer with basic competence.
On the other hand, phone cameras are amazing for their ridiculously tiny size, and their cost is obscenely low after the economies of scale kick in. They take much better pictures on average than the <$50 35mm film cameras from the 1990s, especially when the photographer is a complete beginner (those are the cameras I think of as their spiritual ancestors).