> Then they'll have to find a way to separate the "smart" frame from the prescription lenses, so you can change the glasses when your sight changes without having to buy smart frame each time - or the other way around, upgrade your frames without having to buy prescriptions lenses again.

Ehh, there is nothing special about the lens, all the magic is in the frame, and the rayban and oakley frames look very similar to their standard versions. Getting new lenses for sunglasses is very common.

Have you never had prescription sunglasses?