If you were hoping to save money by using your old iPhone cases you bought for the iPhone 6s and 6s Plus and reuse them for the new iPhone 7 because it is similar in size and structure then we report with regret that you might not be able to do that on account of slight differences that the new iPhone has.
One of the biggest reasons for this is that the camera modules on both the new models are larger and are placed towards the outer edge of the phone. The iPhone 7 Plus has a dual lens camera one of which is a 12-megapixel wide-angle lens while the other is a 12-megapixel telephoto lens.
While the camera on the iPhone 7 isn’t dual lens but is still larger than the camera on the iPhone 6s. Keeping all this in mind Apple has released new official cases both in leather and silicon but if you own an iPhone 6s and 6s Plus bumper case than that would probably fit.
All in all the case wouldn’t fit doesn’t mean that you won’t be able to make it fit. But anybody who is willing to spend that exorbitant amount of money on the new iPhone 7 and 7 Plus shouldn’t mind spending a relatively small amount on the new case which is probably the wiser thing to do anyway.