New Level 50 Content
Extreme Mode Primals
Good King Moggle Mog Primal
One Other New Primal (See note at bottom of post)
One new 4-8 man Level 50 Dungeon (Pharos Sirius)
Two Hard Mode Dungeons
Crystal Tower 24 Man Multi-Part Raid

New Unknown Level Content
New FATES
New Questlines (Including Hildebrand returning)
Beastmen Daily Quests
Treasure Hunting

PvP
Wolves Den Arena PvP
4v4 and 8v8 PvP

Housing
Three housing locations (See note at bottom of post)
Over 220+ Pieces of furniture/etc.
Multiple different settings/etc.
Three sizes (S/M/L)
FC Housing only

Duty Finder
Updates to include a board for seeking party/etc. for each individual server.
Dungeons/etc. Split up into categories.
Bonuses (Tomes) for joining 'random' dungeon selections in each category.
MVP System
Vote-Kick
Dungeon EXP Increased

Free Companies
Updates/Improvements to FC Bank
FC Alliances
Automatic FC Leadership Transfer for extended AFK time.

Beauty Salon
New Hairstyles/Facepaint options
Ability to change Hairstyle/etc. on whim.

Misc
Balance Changes (See note at bottom of post)
WAR Buffs
DRG Adjustments
Melee Buffs/Adjustments to fights to help Melee
BRD Nerfs
Adjustments to cross-class skills
UI Updates/Fixes
Multiple PS3 Updates
Fixes to Focus Target Bar
Inventory Sorting
Improvements to Camera handling
Better item comparisons (Might be pushed to 2.2)
Bunch of other stuff

Note on Extra Primal : Confirmed to either be Leviathan, Shiva, or Ramuh. Some argument exists on which of these it will be.

Note on Balance Changes : Items in the Balance Changes section come from the latest Live Letter, and while these were stated explicitly, it was under comment that the specifics are still in flux, so some may be added or removed as they feel the need.

Note on FC Housing Locations : There are conflicting sources on whether this will be Limsa Lominsa's housing area only, or all three housing areas.

reddit.com/r/ffxiv/comments/1q2cyc/list_of_knownconfirmed_changes_for_21/

Nice! Thanks for the info lance :)

You're welcome, since I'm always scouring the internet I find stuff like this.

New information for Arcanist/Summoners, Pet Macros will be added in 2.1.

New information and major at that. Myths will be increased to 450 a week!

From the initial release of FFXIV: ARR, we predicted it would take roughly a month and a half for the most dedicated players to reach the Binding of Coil of Bahamut, and roughly two months for the general player population. Furthermore, we wanted players to acquire gear using Allagan tomestones of mythology in tandem with clearing the Binding Coil. This served as the basis for determining the rate at which tomestones can be earned, which is currently limited to 300 tomestones of mythology per week. With the release of patch 2.1, this limit will be increased to about 450 tomestones per week, for reasons which will be explained at the end.

Huzaah! Definitely happy with the myth cap increase!!!

Yeah, the increase will make it easier to obtain the harder AF2 gear that requires 3 weeks and now makes it possible in 2.