I'm sorry, but given most of the hardware is unchanged from an overhaul-in-technology perspective (e.g. this isn't first year for dual-lense camera on the Plus model), I would find it extremely irresponsible of Apple to have either 8 or 8 Plus supply this year.
We can make this argument about almost any year over year upgrade. But what about those upgrading from two or three years back? Not everyone on the planet if on the same generation cycle. There will always be 10's of millions of people looking to upgrade from phones two years old or greater.
Also, I think its a bit short sighted to say the hardware is unchanged. This isn't the first year a single lens camera on the non-plus model either. There are plenty of upgrades from the 7 to 8 that people coming from older models would like.