If it has a dual camera you can bet that it will produce much better images. But you are correct that at this stage we don't know what it will be used for, or even if the dual camera will be in the device, Apple could change their plans or it could of just been an incorrect rumour.
From my point of view (and probably a few other people from what I've seen) it will be worth the upgrade because I have the 6 Plus, so moving forward to the 7 Plus would be worth it because not only will I get 3D Touch, Live Photos, a better 12MP camera and 4K video BUT also what ever features the 7 and 7 Plus have, despite all the rumours you can bet that the 7 will have new features that is a given, Apple knows that they need to give people a reason to upgrade no matter how small or how big.
The reason I created this thread was for the iPhone 7 leaks and rumours, so that people could post and talk about them and what they think. Just thought it would be better under one thread 🙂