I still don’t believe that they’ll show exclusive features for a device that hasn’t even been announced yet. The iOS 18 Generative Features that’ll get announced at WWDC will be available to all devices that can run iOS 18. Any exclusive features will be announced in September, when the devices that can run those features will be announced. Unless, you know, Apple decides to randomly announce the iPhone 16 lineup at WWDC for some reason.
I'm pretty sure that at WWDC they'll announce iOS 18 features that are "coming later this year" and then limited to iPhone 16 (Pro). Probably the coolest features.