For one thing, we know that the current models on the PTR are mere placeholders. Currently using a hodgepodge of Tier 8 sets and off-pieces, one of the things we can all look forward to is when Blizzard finally unleashes the actual new tier gear designs. The difference between this set of tier gear versus all others that have come before it? They will be faction-specific, which is a first for PvE armor sets. Patch 3.1 introduced faction-specific PvE weapons, and they looked totally awesome. If the designers keep that same creative energy when designing the armor sets, we're in for a real treat.
Thanks to faction-specificity, Patch 3.2 also introduces a new naming convention for tier sets -- each one is an homage to a particular character in World of Warcraft lore. That in itself is pretty cool and exciting. As Michael Sacco puts it, at the very least the armor sets shouldn't be shared across armor class the same way gear from Sunwell Plateau and consequently Arena Season 4 made players look generic. Hopefully there's none of that and the new tier gear will blow us all away.
The Death Knight tier gear for Alliance is named after Thassarian, the first Death Knight to join the Alliance. By the same token, the Horde's Death Knight set is named after Koltira Deathweaver, speculated to be the first Horde Death Knight. Both figure heavily in the Death Knight starting experience and Thassarian's origin will be explored in an upcoming volume of Tokyopop's Warcraft Legends manga. There are two distinct sets of armor, the DPS version and the tanking set. You can check out the set bonuses (which aren't indicated in the PTR items) over here.
Alliance Druids get the better deal here as their Tier 9 set is named after Malfurion Stormrage, arguably the greatest Druid (or Arch Druid) ever and one of the most powerful beings in Warcraft. Although he has yet to make an appearance in the game, speculation is rife that we'll all see him very soon in the next expansion. Horde players don't get a set named after a near god-like being, but they do get to honor Arch Druid Hamuul Runetotem, the Horde's premiere tree-hugger. He's no pushover, as the first Tauren Druid in over forty generations was taught by Malfurion himself. The Tier 9 sets come in three natural flavors: Balance, Feral, and Restoration.
It gets a bit confusing here because Tier 9 is the first Hunter tier set to break from the -stalker nomenclature and apparently both the Horde and Alliance sets are named Windrunner. However, the Alliance set is actually an homage to Alleria Windrunner, the eldest of the famous Windrunner sisters and a reknowned Ranger. While she has yet to make an appearance in the game, her younger sister Sylvanas has held sway over the Horde's Forsaken from day one. The Horde's tier armor is named after the Forsaken leader and if the gear looks anything like her redesigned armor, we just might have a -- pardon me -- horde of Horde players lining up to have their genders changed to female. Check out the Windrunner set in the gallery.
The Alliance Mage set is named after Khadgar, the kindly old geezer in the middle of Shattrath. He was an apprentice of Medivh himself and this mega-powerful wizard had a prominent role in the Second War. Horde players get their set named after a Sunstrider, though it isn't quite clear which one. The most likely candidate would be the hero-turned-villain Kael'thas Sunstrider, who was a high-ranking member of the Kirin Tor. But as lore guru Alex notes, it could really be any of the Sunstriders, a long, noble line of magic users. Khadgar's Regalia is in the gallery, too.
While many sets are named after the first person of a particular class, Alliance Paladins have their set named after the Paladin hero Turalyon, an apprentice of Uther the Lightbringer, who figures more prominently in the World of Warcraft. Although absent from the game like his consort Alleria, his statue can be prominently seen at the entrance to Stormwind holding Anduin Lothar's broken sword. The Horde get a relatively new figure in lore, Lady Liadrin, who was the first Blood Knight or Horde Paladin. The Paladin Tier 9 sets come in three Light but filling variants: DPS, healing, and tanking. The set bonuses aren't on the items in the PTR, but you can check them out on Eliah's list.