With the coming of Wrath of the Lich King, Blizzard has made it clear that they are changing the loot system so that more classes share gear. Their motivation is certainly rational. Who wasn't sick and tired of having Boomkin, Elemental Shaman, or Ret Paladin gear dropping when one of these specs was not present in the raid.
Here's a useful list of the new gear "classes" that will most likely be present in WotLK. My main point is coming after the list.
Caster Cloth - Intellect, Spirit, Spell Power, Crit, Haste
All specs in the Priest, Mage, and Warlock classes will be interested in these stats, with DPS also interested in Hit, which could be provided by things such as trinkets, enchants, or gems.
Caster Leather - Intellect, Spirit, Spell Power, Crit
With similar stats to the caster cloth armor, this class of armor will interest Resto Druids and Boomkin, with Boomkin also interested in Hit and Haste (I don't know if Resto Druids will want Haste or not).
Melee Leather - Agility, Attack Power, Crit, Haste, Hit, Expertise
Just like right now in The Burning Crusade, this armor will interest Rogues and Kitty Druids.
Physical DPS Mail - Agility, Intellect, Attack Power, Haste, Hit, Crit, and some MP5
With the Enhancement Shaman changes that will make Agility worth 1 Attack Power in addition to crit, this armor will interest Enhancement Shaman and Hunters alike. Enhancement Shamans will also make use of Expertise.
(As an aside, can mobs dodge ranged attacks? Is Expertise useful for Hunters?)
Caster Mail - Intellect, Spell Power, Crit, MP5, Haste
This set of caster armor switches out Spirit for MP5 since it will be for both Resto and Elemental Shamans, who have no use of Spirit. Elemental Shamans will also make use of Hit.
Melee Plate - Strength, Crit, Haste, Hit, Expertise
This will interest all Death Knights, DPS Warriors, and Ret Paladins, though Ret Paladins may want some MP5 depending on the Mana provided by their upgraded talents.
Tanking Plate - Strength, Stamina, Dodge, Parry, Defense, Hit, Expertise
All plate wearing tanks, the Death Knights, Tankadins, and Protection Warriors, will be interested in this gear.
So, did you see what I saw? There are tho specs that do not show up anywhere on the above list, because their gear needs do not match those of any other class in their armor type. These specs are, of course, Holy Paladins (Plate - Intellect, Spell Power, Crit, MP5, maybe Haste) and Bear Druids (Leather - Stamina, Agility, Dodge, Attack Power, possible Parry if Blizzard allows Bears to parry).
Will these two specs become the redheaded stepchildren of the loot tables, with every other spec groaning when Holy Paladin or Bear Druid gear drops? Or will Blizzard come up with a way of making these specs viable with the above mentioned gear types?
If anything, Bear Druids will share the gear with their Kitty brothers and the Rogues, but this could put them at a disadvantage versus other tanks when it comes to total health and mitigation. As for Holy Paladins, we do share the same stats as the Caster Mail specs, but I'd rather not sacrifice my armor if possible. While I'm against wearing cloth, leather, or mail if the item is an upgrade, I would oppose removing all plate healing gear from the game.
In the coming months I'll keep an eye out on what Blizzard will do.
Edit: After writing this article on the 4th but holding off in order to do some more research, WOW Insider posted a similar one on Bear Druid itemization in WotLK.
Edit2: My research has shown that there is a decent amount of plate healing gear in the beta, which suggests that Holy Paladin gear will be the only gear that only one spec has any use of.