That was my take on it, Mithfindel.
Caldanese would be the widely-understood language used across the State, or more properly the language family most common in the State. With so many people and places, dialects and sister languages would be common. Napanii would be the antiquated form of "pure" or "proper" Caldanese that was used on Caldari Prime pre-spaceflight.
Edit: Another thought- it may be most appropriate to assume the versions of these languages that capsuleers are likely to speak are the "space dialects". There are millions upon millions of people living on space stations and ships in New Eden. With the specialized vocab needed, unique international culture, and confined (relatively) environs of ships and stations, that's plenty of fertile ground for any language to develop a new offshoot in space.