Coming up in WOW: CATACLYSM we are getting new RACE/CLASS combos and it's about time. Should add some flair to teh game as well as that much needed content that has been lacking in recent months (for the non-raider)...
I'm going to go through all the new RACE/CLASS COMBOS and talk about the feasability and lore constraints therein.
HORDE COMBOS
Orc Mage: Why not? Intuned with nature and/or the magics of the world. I can see some Area of Effect leveling in the Cataclysmic Barrens, unless, of course, there are alot of fire and ice resistance critters that come with elemental upheavals as such.
Undead Hunter: Aside from being dead, I'd assume they wouldn't be all that numb to the world... As per usual; Undead look pretty interesting as any class combo.
Tauren Priest & Pally: Tauren are a piece loving and kindly race, I can definately see why the Light has taken them into the fold. Unlike those filthy filthy Grimtotem...
Troll Druid: Bout time. Laidback friendly nature dwellers. It's good to see more Druid playable races. I think Dwarves have plundered the depths too much to gain favor with nature. One would think, at least.
Blood Elf Warrior: All races should have the warrior capacity. The Blood Elf were stated as being 'too weak' in previous patches. I was fine with that, as The Light may imbue them with the power necessary to lift a hammer.
Goblin can't play Druid & Pally: Makes sense as they are unscrupulous business peeps... may have wronged nature in the past. One would think that they could be paladin as well, as they can be Priests, but, y'know... whatever. Welcome aboard boys, bout time.
ALLIANCE COMBOS
Human Hunter: Sure, why not?
Dwarf Mage & Shaman: Obvious fit as they are one with the earth and all that... probably gained Mage skills through their recent interaction with the Humans and the such... The Drano probably brought with them Shamanistic traditions. I'm sure they get along real well being gemcrafters and all that.
Night Elf Mage: This kind of magic is usually frowned upon by the Night Elves... Warlocks would be a no-go for the Nelves, but (depending on the book) mages draw their power from the Elemental Planes and not from the magics of this world... Mana as an energy source doesn't fit well with Night Elf Lore.
Gnome Priest: Seems like The Light hasn't fully forsaken the Gnomes. Bout time as they've had like 4 classes for the longest time with little to no variance in gameplay (2 casters, 2 melee: Lock/Mage, Warrior/Rogue). I think Hunter wouldn't be too far from their range... not sure if the Tech Head aspect of things would keep them completely out of the woods. Yet again, they're out of the cave much like their Dwarven breathren. They are going to be a terrifying force to be reckoned with in BGs as they can hide pretty much anywhere.
Draenei: No new classes for the Draenei this time. Druidism wouldn't be out of the question, albeit it would take their worship away from The Light. No Rogue or Warlock as those classes tend to draw the filthy dirty races of the world to their ranks.
Worgen CAN'T PLAY Paladin & Shaman: But they can play priest. I'm not sure if this is a game balance or a Paladinian forsaking of the light (as they are cursed with Worgenisism). As they were Human before, a lack of Shamanism does make sense.