Okay, so the only thing we have here...
New A10 chip - Almost double the speed of the 6, fine, but great games run fine.. could wait till next year.
Storage Capacities - Doesn't really matter if you like your current storage capacity.
Color Options - Superficial, just color.
Water Resistance - Superficial, I can shower without my phone just fine.
No headphone jack - I'll let early adopters adjust to it for a year, I can wait on that.
earpiece receiver becoming a speaker - Okay, but my iPhone sounds fine now. Can hold out till next year.
Clickless home button - nice, but just a new touch.
Wide color displays - Nice, but am I happy with what I have now? its good enough.
Dual lens rear camera - This is definitely very useful WANT.
Upgraded rear camera flash - Flash, photos look better wtihout it.
Upgraded proximity sensor - Not that big of a deal.
FeliCa NFC - Don't make so many contactless payments.
So in the end, it really boils down to the Camera, new A10 Chip, and better color displays.
Give the iPhone 7 is a new release, any slowness from new apps that push the processor to its limits probably won't have negative on the 6S at least within the 1st year of its launch.
This makes Camera the only thing that I really care about. Given the cost of the iPhone and major redesign coming next year, I think this still justifies the "okay to wait till 2017" stance!