So, I've been thinking a bit lately about how I believe SE has set a precedent for other job progressions in the future, based around how they designed the Arcanist class branching into the Summoner and Scholar jobs.
It seems to me that they are possibly establishing a pattern to introduce other jobs down the line, following this same path.
So, here are my predictions, and I'd love to hear what you guys think! (I've left Arcanist off, for obvious reasons)
Archer -> Bard and Ranger (or Musketeer/Corsair)
Conjurer -> White Mage and Geomancer
Gladiator -> Paladin and Red Mage
Lancer -> Dragoon and Samurai
Marauder -> Warrior and Dark Knight
Pugilist -> Monk and Ninja
Thaumaturge -> Black Mage and Time Mage
Obviously, these are suppositions and guesses... but also seem like they could hold a possibility of coming to fruition.