Now that I think of it, they could include the FaceID projector (which is the part that needs to be thicker) in the chassis (like some laptops that include the webcam near the keyboard instead of on the lid) to project the beams used to identify face shape but still the camera/FaceID pattern reader on the lid (which is a better suited angle for making people look good). That *might* be possible.Yep, unfortunately without a redesign Face ID is highly unlikely, and perhaps not even then. The hold-up for both Face ID and higher res webcams is the thickness of the lid, which currently couldn't fit a much higher-res camera, not to mention a true-depth scanner. It's hard to imagine Apple accepting additional millimeters across the entire lid just for the webcam.
Where there is the potential for some improvements, I imagine, is if Apple were to apply some of their software camera magic from the iPhone to the webcam. It may be that the Mac A-series chips still include some version of the photo processing unit on the phones, and I've wondered if they might not try to improve webcam performance that way. Maybe there's even some less-hardware-based form of Face ID in that. I wouldn't expect anything like either though until the probably 2021 redesign at the earliest.
The iMac, on the other hand, I would find surprising if it didn't have Face ID and a better webcam.
As for a less hardware-based version of FaceID, that's a no-no. It would be much less secure.