My 2nd and 3rd job predictions of the current classes would be
Archer -> Ranger: Sustain DPS (Single target focused)
Archer -> Sniper: Pure DPS (Single target focused)
Arcanist -> Avatar: Pure DPS (Uses carbuncle as main pet. Summons the Primals as combo finishers. Primals are AoE focused.)
Conjurer -> Geomancer: Support Healer (Gives spike shields to tanks)
Conjurer -> Bishop: Hybrid Healer (Shields a lot and AoE Heal bursts with Prayers)
Gladiator -> Fighter: Pure DPS (Dual-Wield. Single target focused)
Lancer -> Dragonkin: Sustain DPS (Pet class. AoE capable)
Lancer -> Templar: Balance Tank (Elemental Breaths for Single and AoE.)
Marauder -> Viking: Sustain DPS 2H Broadsword instead of Axes (AoE capable).
Marauder -> Berserker: Pure DPS 2H Greatsword (Single target focused.)
Pugilist -> Dancer: Support DPS (combo finishers buff certain roles. Single target focused)
Thaumaturge -> Illusionist: Heavy Armor Sustain DPS (AoE. Ground target focused.)
For new classes 2nd and 3rd job predictions
Gunner -> Musketeer: Pure DPS (Single target focused)
Gunner -> Flintlock: Sustain hybrid (AoE capable and with enemy debuffs and friendly heals)
Rogue -> Thief: Sustain DPS (Single target focused. Dual-Wield)
Rogue -> Ninja: Main Tank (Single target focused uses evasion and clones to avoid damage. Dual-Wield)
Rogue -> Assassin: Pure self-sustained DPS (Single target focused. Dual-Wield)
Ronin -> Samurai: Pure sustain DPS (Single target focused. 2H Katana)
Ronin -> Shogun: AoE Off-Tank (High HP AoE Tank. Uses Guard and Threaten to support Main Tanks)
Spellblade -> Dark Knight: Self-sustain DPS (AoE capable and debuffer)
Spellblade -> Rune Fencer: Pure DPS (Single target focused and buffer)
Spellblade -> Runeseeker: Hybrid Healer (AoE focused healer and buffer)
Animist -> Blue Mage: Hybrid DPS (Diverse.)
Animist -> Beastmaster: Pure DPS (Diverse.)
Animist -> Morpher: Sustain DPS (Diverse.)
Sage -> Red Mage: Support DPS (Buffs other roles with infused elements. Stone increases det, Wind increases crit, Water increases speed. Double casts and moving cast)
Sage -> Time Mage: Hybrid DPS (Single target focused. Tank LB)
Juggler -> Puppetmaster: DPS hybrid (Diverse)
Would look forward to "sub jobs" being introduced.