I'm also sceptical about an external amp module for Ultima since it's already a very long device. With an AMP, how long will it get? It's already less pocketable than AK380. I though they are rather planning accessories like dock, recorder maybe, etc.
.... or a "extra storage module". A slim module with an additional 1 Tb, without all thoses USB-c cables and extra charger needed, will be great.