Alchemist (ALC) is already in FFXIV - it's a Disciple of the Hand though and is not a battle class (it makes potions and medicines). And we're getting Samurai (SAM) in Stormblood. Songstress is just BRD with a different name. The others are just gimmick jobs that don't suit a MMO environment (like Berserker, which was an old Job from FFIII and V that... basically just attacked uncontrollably for high physical damage. It's pretty easy to see this simply would not work in FFXIV. And Gun Mage is just MCH with elemental bullets.).

SE will continue to add new Jobs to the game (I mean, in a week's time we're getting SAM and RDM already), but ones they know can fit into the game's lore and MMO mechanics, and especially ones that don't just merely rehash an existing class's abilities or role in a party. Many of FFX-2's Jobs are meant for FFX-2's battle system and storyline, and so just would not work here I'm afraid.