Apple typically doesn’t even know what their final designs will look like until like 6 months before release. Anything can change between now and next year. If your phone fulfills your needs now, wait. We’ve been on this gravy chain for over 10 years now.
Also, the way Apple realeases phones is by trickling features. Every single phone has some kind of feature they will tout in marketing. Touch ID, 3D Touch, Telephoto lens. Google, however, throws everything but the kitchen sink in their phones (sometimes drowning out really good features).
I’ve had iPhones since the 4S. Realistically, there hasn’t been a change so earth shattering that it immediately made others obsolete (perhaps when they went lightning). I probably would still have had my 6 if the processor wasn’t under powered.