I agree, FFXIV:HW is a new game, the story continues but the game is new.
Logically SE wants to attract players to buy the game. The New 3 Jobs are the basic starters for the new game.
I think they'll have a starter Lv.25 to 30, but they won't have any access to FFXIV:ARR map nor content.
As I see a new adventure -from scratch- starting in Ishgard is very logical compared with the conclusion of main sscenario of 2.55.
