Ishgardian themed jobs, Dark Knight obviously fits that bill very well, and could possible branch off of a Templar or Temple Knight class. Lore wise being a rogue knight learning the dark arts.

Chemist would work well with the castle themes aswell for a healer.

Maybe we'll get a grittier take on Musketeer as opposed to pirate lark we've seen up until now (although that's a long shot (pun slightly intended))

Geomancer or Necromancer has a good aesthetic for the expansion.

They also mentioned a lot of Beast Tribe run areas, maybe this could lead to Beastmaster or Blue Mage. (Grasping at straws here)


Slightly off topic; I'll be incredibly surprised if we don't see Alexander as a summon at some point during the expansion.