If you watch the Gruber show/interview, the Apple execs go on about how core EyeSight and what it represents is to the product and to Apple. They can’t exclude it on any headsets now. Maybe a cheaper solution but the essence has to remain.
I've considered that. Potentially, it could be replaced by a HomePod-like blurred lighting apparatus to show the state the user is in, whether they can see you and you can speak to them vs being in a completely isolated state, rather than displaying their eyes directly.
The EyeSight assembly is an entire other device. It's not just a display, it's a system that reproduces your eyes and shows slightly varied versions in each direction, using a cutting edge curved lenticular display. That's an obvious target for getting the cost down, possibly by close to $1000 for that assembly alone.
But yes, I see Apple's motivation for EyeSight, and if they can find a cheaper way of doing the same, I think they'll do that rather than a fully opaque front. Ultimately, having a transparent interior display with variable occlusion would allow for discarding EyeSight entirely as you'd see through the front glass when they're in AR but that would be something to appear in the more expensive VisionPro first, then make its way down.