If "ShrimpApplePro"'s rumor is true, that would mean the only part of the Face ID hardware that might move under the display for the 18 Pro models (though maybe not yet for the non-Pro models) is the infrared 3D dot projector, but the IR camera itself that detects those IR dots bouncing off of your face might retain its visible lens within the Dynamic Island cutout/pill, meaning we'd be seeing a shorter pill shape rather than a circular hole punch for just the visible light selfie camera.
Due to the longer wavelength of IR light and how it interacts with smartphone display pixels, there are more technical challenges to getting Face ID's IR camera and its lens under the display and have them work properly, than for putting the IR dot projector under the display first, though moving the IR camera under the display is rumored to come in later iPhone models, possibly 2028 rather than for any of the 2027 anniversary models if Apple can't overcome the hurdles by the time they start making the 2027 models. If that's true, then Apple's roadmap for moving both cameras under the display might “plateau” for a couple years after the dot projector move for the 2026 Pro models, and the 2027 anniversary model's most visible redesign might be limited to just the bezel-less "all-screen" approach we've been hearing about, but if it still has a small DI cutout, that would make it harder to call this an all-screen design.
But thinking about it, how likely is it that Apple will want to "delay" putting both front cameras under the display until the year after the 2027 anniversary model? My guess is that Apple might be pulling out the stops for trying to get both front cameras under the display as early as the 2027 anniversary model, but physics and the supply chain might limit them to 2028 anyway. Whatever happens, Apple will still produce the other, non-anniversary iPhone models in 2027, and cram most of their new technology into only the anniversary model.