Seems like you’re missing a few options. You mention a potential for the display to be embedded in the lenses later in your article, which if the lenses are prescription lenses, glasses wearers can rejoice (Glass was doing this). Prescription lenses could also be snap on, like snap on sunglasses.
Sunglasses can be handled the same way with clip ons. Or, there are a few technologies that change the opacity of lenses that could be used too: light based opacity and electric current based opacity.