Extremely unlikely, I'd have thought.
Judging from the prototype, the whole top casing is different. And inside, the main board will need new connections for the screen, buttons, camera, &c. (And that's without considering the different processor and other chips, NFC antenna, further Android customisation, &c.)
So no, I'm fairly sure you won't be able to 'upgrade' a Gemini without replacing most of it. Sorry...