Your situation might be different in that you have an existing version that some people might have bought, but testing for iOS versions before 8 is difficult and time consuming. Not to mention that we talk of a group of users who are fewer and fewer as time progresses. iOS 10 is around the corner, so supporting older versions is less and less useful. I have an old iPhone 3s, but I can't even connect to the appstore with that one - expired certificate or something like that.
I know Cocos2D 3.4 retains compatibility code for iOS 5 and iOS 6 but I personally would never start a new project supporting anything than iOS 8 at the earliest. And once iOS 10 is released, my target would be iOS 9+ (because when the project is done, chances are that the next OS version is just around the corner)