All four iPhone 16 models will have A18 chips
Last year Apple launched the iPhone 15 and iPhone 15 Plus with the A16 Bionic chip, and the iPhone 15 Pro and iPhone 15 Pro Max with the A17 Pro, introducing even more differentiation between the Pro and non-Pro models. This wasn't very well received, and it turns out to be an especially egregious move in hindsight now, when you consider that only the iPhone 15 Pro and iPhone 15 Pro Max support Apple Intelligence, precisely because of the chipset.
The good news is that it seems like Apple isn't going to do the same thing this year. According to code discovered in Apple's backend, all four iPhone 16 models will be powered by an A18 chip.
There might still be a two-tier system, where the non-Pro iPhone 16s get the A18 while the Pros get an A18 Pro or something like that, but at least the cheaper devices won't be stuck with last year's SoC.
If Apple does go the tiered way, then the vanilla models might get a smaller number of GPU cores, either binned or disabled. The interesting bit is that five models were discovered in Apple's code, and it's still a mystery what the fifth will be - speculation says it may very well be the next iPhone SE, which could launch in early 2025 with the same chip as the iPhone 16 family.