Changes in Patch 2.2 (Maelstrom)

Under construction. Please help edit/add to the list!

Confirmed for 2.2

New Coil turns which drops new Allagan gear [source]
Leviathan (hard mode and extreme) [source] [2]
1 new dungeon (ruins of amdapor) [source]
2 new hard mode dungeons: Brayflox + Halatali [source]
New Hildebrand story [source]
New story missions, probably leading up to Leviathan. (source needed)
Extreme mode King Moogle [source]
Kobold and Sahagin dailies [source]
New currency like Philo and Myth (source needed)
New artifact armor (source needed)
Vanity system (Mirage Prism) [source]
Expansion of the dye system (source needed)
Crafters will be able to alter gear designs using a “template” system (official name TBD) [source]
Wait command in macros will be allowed in-line. [source] [now in patch 2.16]
Free Company alliances [source] [2]
New hair styles (Yoshi-P has said each major patch will have a main focus on a single race) (source needed)
Ability to indicate number of items to store in a retainer [source]
A retainer can be hired for a Free Company's estate "From patch 2.2 onward" [source]
Ability to hide (again) quests from the HUD duty list [source]
Change luminary Workbench and table visuals [source]

Confirmed to be coming, unconfirmed for 2.2

Echo buff added to older content (Including Coil) [source]
Frontlines PVP system [source] (unconfirmed for 2.2, but mentioned to be around 2.2 or 2.3)
Personal housing (Most likely not in 2.2) (source needed)
A third retainer (source needed)
Ability to queue for Crystal Tower with 24 people (source needed)
Addon support (Originally mentioned to be 6 months after launch. Currently unconfirmed for 2.2 though) (source needed)
64-bit clients (Confirmed to be built due to development for the PS4 being 64-bit as well. Currently unconfirmed for 2.2) [source]
DX11 to be added well after 2.2, even after the next expansion [source]
4k Resolution support [source @5:16]
Ability to queue in duty roulette with multiple people [source]
Chimera and Hydra added to duty finder [source - patch 2.16]
Teleport map [source]