So, we now have 11 classes in WoW. In stands to reason that Blizzard would want this game to end with 12 classes. Its generally not a good idea to end things off on an odd number. Of course the argument could be made that Blizzard can do whatever they want, and a 12th class may never appear in WoW. With that said, let's just assume that Blizzard is going to make a 12th class; What could that class possibly be? Well, let's look at the pattern of class implementation since TBC;
Death Knights: Filled the archetype of a Dark/Evil knight. Filled the missing scourge heroes from WC3. Filled the void of the ever popular Necromancer class. Went extremely well with its expansion. Filled in the third plate slot. Was a great counterbalance to the very popular Paladin class.
Monks: Filled in the archetype of Martial Arts fighter. Filled in third leather slot. Went a long way to improving Tank and Healer diversity in the game. Unique style and abilities fit in well with the general WoW class structure. Perfectly utilized the WC3 hero's abilities.
So what's left in WoW? What could the next class in WoW be? While numerous ideas have been tossed around, my theory is that the next class will either be Rangers or Tinkers. Here's five reasons why;
1. Ranged Weapons and Mail Armor
This factoid has been beaten to death, but its a well known fact that there's 2 glaring voids in current WoW class balance: Hunters are the only class that can fully use Guns and Bows, and that only 2 classes currently wear mail armor. Every other armor set is currently at three classes apiece. Hunters are also very powerful because they are the only class that are physical ranged. They hit faster and harder than magic users, and can kill you from afar. In battlegrounds and world PvP, Hunters are absolutely devastating PvP opponents (a different story in arena though). No one can match them. Bringing in another class can finally give them the competition they deserve.
Also bows and guns are cool. Other classes should be able to wield a gun and a bow than just a hunter.
Mail armor is also an issue. Hunters use AGI Mail, Shaman use AGI and INT Mail. This provides a great opening for a mail using class to enter the game.
Hunters are the most popular class in the game by a wide margin. They're powerful, have lots of abilities, utilize numerous types of pets, etc. Also archers and bow users are popular archetypes in RPGs and other media. Legloas from Lord of the Rings, and Hawkeye from The Avengers are just two such examples. I'm sure this isn't lost on Blizzard, trying to find ways to bring in new players. I'm also sure you've had numerous players looking for that archer class, only to see that you had to drag a pet along with you.
3. WC3 Hero factor
There's quite a few WC3 heroes left that could help flesh out these potential classes. Goblin Tinkers, Dark Rangers, PotM, Dryads, Goblin Alchemist, Wardens, etc. could all be utilized to create the new class. For the Ranger pool alone we can pull abilities like Sinister Strike, Searing Arrow, Scout, Frost Arrow, Charm, Vengance, Abolish magic, and Mana flare. Toss in some abilities from the Diablo 3 Demon Hunter, and we have the makings of a pretty strong class template.
Tinkers are also pretty varied. You can utilize the abilities from Goblin Tinkers, Goblin Alchemists, Sappers, Shredders, and numerous examples of Tinkers in WoW. The Engineering archetype for RPG classes is almost as large as the Archer's.
4. The Race Factor
I'll keep this one brief; Several races can be Tinkers or Rangers/Archers. Also they don't have a significant appearance or weapon requirement to make them "feel" like they're the proper class (unlike another proposed future WoW class). This gives the classes significant flexibility in terms of implementation.
5. Hybrid Vigor
Tinkers have this as a slight advantage over Rangers. Its pretty easy to make a Tinker into a tank via their affiliation with Robots and machinery. I mean, what better tank for a dungeon than an actual tank or giant Robot? They can also heal because obviously technology improves medicine by default. A more advanced army also has more advanced medicine. This could help make Tinkers feel a bit different than already existing healing classes that use magic to heal.
Rangers could also heal, since they'd be more than likely users of nature magic. However, tanking would be a bit more difficult to pull off since we're talking about a ranged class. Regardless, I don't see another pure DPS class entering this game given the queue problems with LFR and LFD. Blizzard will more than likely stress a class that can do more than one role. Given that, both classes could potentially be implemented as any hybrid combination.
In the end, I feel that Tinkers have a large advantage over Rangers. They can be made to be a lot more distinct than Hunters. They can easily be made into a tri-spec (Tank/Heal/DPS) hybrid. Finally, they would be unlike any other class currently in the game. The main drawback for Tinkers would be their closeness to the Engineering profession. However, it shouldn't be that difficult to differentiate a class from a crafting profession. Robotics, Chemicals, Gunpowder, Magic-based tech, Steam, and gadgetry are all aspects that can be explored for this class. Also Tinkers have been shown to fight in melee range;
Rangers have the advantage of not being associated with a profession, and having a large archetype to work with from WC3, Diablo 3, and RPG lore in general. The problem for Rangers is making them completely distinct from Hunters. I mean, you're going to have to make them really different from the Hunter class to make their implementation work. Simply removing pets isn't enough. A melee spec and a healing spec could help, but even then, some overlap is possible.
Despite those drawbacks, those classes have the best chance of entering WoW as the next class. Clearly Blizzard could create a completely different class than these two, or maybe even a combination? We'll just have to wait and see.