Just to ground people a little in size....
Almost all of the talk is about a ship that is somewhere in the Voyager to Freedom class ships- which is between ~3600 to 4600 passengers. Just for fun, stick with Voyager for 3600 passengers.
This compared to Vision (2200) or Radiance (2500).
So at a min, the ship needs about ~500 more cabins at double occupancy. Sure, you can stretch it like the Enchantment- but that added ~150 cabins.
The only choices are to make it wider or higher for those added cabins.
Wider is very possible, but it would end up limiting the places they can go, too. So higher is the most likely thing. That's multiple decks higher. Have to be a heck of a stack to retract multiple decks in.
I want it to be true, too. As we really enjoy sailing out of Baltimore. But realism of what they are actually saying suggests that the ship isn't likely to be that small.