There are currently eleven playable classes in-game:
Death Knight, Druid, Hunter, Mage, Monk, Paladin, Priest, Rogue, Shaman, Warlock, Warrior
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They perform these roles:
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5 Tank (Monk, Death Knight)
5 Healer (Monk)
7 Melee Damage Dealer (Death Knight, Monk)
5 Ranged Magic Damage Dealer
1 Ranged Physical Damage Dealer
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Roles that have never been added with a new class is:
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Ranged Magic Damage Dealer
Ranged Phsyical Damage Dealer
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They wear these type of armors:
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3 Plate (Death Knight)
2 Mail
3 Leather (Monk)
3 Cloth
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Armor that have never been added with a new class is:
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Cloth
Each new tier armor design comes in a form of no class restriction in LFR or other difficulty.
So it's just the mail users now being Shaman and Hunter, that is "losing" one tier design to copy from for transmog.
If transmog is important for you, then it might be important for Blizzard to "balance" it.
And since we have no new class of Ranged Magic Damage Dealer or Ranged Phsyical Damage Dealer..
That's why I believe, we will see the next class to have at least one of these roles.
Also, I think it is important to remember that both the Shaman and Hunter share mail with agility, but does not share mail with intellect on.
Shaman has mail with intellect, only for itself.
Based on this, my conclusion is .. we will see a new class that wears mail with intellect on, for dealing damage (either Ranged Phsyical Damage or Ranged Magic Damage), but I have great belief that it would be Ranged Phsyical Damage, because there is no class system that uses Intellect and Ranged Phsyical Damage.
Also, I have little faith they will possibly make a new special class of developing a way to deal Ranged Damage Phsyical - through the use of normal weapons like swords.