Not seeing much point upgrading to the 7s to be honest given the rumors it will only really include glass back from last years model. The OLED iPhone is where we will see improvements.
The OLED model is where you see the latest technology, both phones will have improvements. The 7s Possible features: Wireless charging, camera enhancements, A11 chip, Tru-Tone, Improved water resistance, new colors, etc. For some, the 7s will be more than enough to upgrade from an older device and will have a lot of popularity with the price point.