Taken from here: http://www.reddit.com/r/ffxiv/comments/1q2cyc/list_of_knownconfirmed_changes_for_21/
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 Questlines (Including Hildebrand returning)
Beastmen Daily Quests
Wolves Den Arena PvP
4v4 and 8v8 PvP
Three housing locations (See note at bottom of post)
Over 150+ Pieces of furniture/etc.
Multiple different settings/etc.
Three sizes (S/M/L)
FC Housing only
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.
Updates/Improvements to FC Bank
Automatic FC Leadership Transfer for extended AFK time.
New Hairstyles/Facepaint options
Ability to change Hairstyle/etc. on whim.
Balance Changes (See note at bottom of post)
Melee Buffs/Adjustments to fights to help Melee
Multiple PS3 Updates
Fixes to Focus Target Bar
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 weather this will be Limsa Lominsa's housing area only, or all three housing areas.
I might be an onion thief, but I'm still a thief.™