Apple can even argue that AI requires both 8GBs RAM AND also the added neural cores that are rumored to the next iPhone SoC.Ah the only updates everyone with an iPhone 14 series or below will be getting.
AI is for 15 series only, thanks to Apple skimping on RAM for years and no actual direction or vision.
My best bet, however, is that most iPhones, even those several years old, will get the bulk of or all AI features. But nothing will be done locally, on-device, all of it will require sending and receiving data from Apple's AI server.
iPhones 16 Pro will perform all or most AI stuff locally, on-device, and therefore much faster with less of an impact power usage.
So, it's not the lack of AI that will make you want to upgrade to iPhones 16 and newer. It's going to be how slow it performs and how much battery it drains by constantly sending and receiving data to Apple's servers.