If you think about it, with all the rumours about the 7, will it look exactly like there 6 and 6s? sure in terms of design shape it will, but with a bigger camera, dual camera on the 7 Plus and the redesigned antenna bands, it will look a little different. It's not like Apple are using the exact same as last year without even twerking it.
Also if the home button rumours are true, will the Force Touch home button look different? personally I'm still looking forward to the iPhone 7, mainly the dual camera and the features that were in the 6s (i'm stilling using the 6 Plus) so I'm sure people like myself will be interested in the 7. Will it be enough for them to upgrade, that will be an individual thing, some people it will take less to upgrade (much like myself) others it will take more. Only time will tell, we will have to wait and see what Apple announce, hopefully soon 🙂