Let's play a small game in here.
Let's speculate what future warfronts could be added to the game.
If possible, list the Warfront you think is going to be added and provide a reason for the fight.
So as an example...
Arathi Highlands: The Horde and the Alliance clash over the immensely strategic city of Stromgarde, the Horde to assist in it's efforts to reclaim the Undercity and the Alliance to prevent the Horde doing just that.
One ground rule is of course that Warfront Barrens is pretty much a given at this point, but feel free to list the reasons you think it's become a point of contention. It's pure speculation, so make up any story you wish.
I believe that we will end up with four warfronts total, including Arathi. So having said that, here are my guesses.
Warfront Southern Barrens: At some point, the Alliance will score a major symbolic win by securing Dustwallow Marsh and rebuilding Theramore as a symbol of Alliance might. Theramore might look exactly as it did before or it could be a new Night Elven city or it could be some kind of hybrid, but it's put back on the map. To secure Theramore and the Alliance presence on Kalimdor as well as to threaten the Horde capital of Orgimmar, a drive is made into the Southern Barrens. Horde forces rush to meet the threat.
Warfront Ghostlands: Blizzard takes the opportunity to update Quel'thalas, making it flyable and bringing the zones onto the Eastern Kingdom map rather than Outland (because the Draenei starting zones are an isolated set of islands, they don't need to be afforded the same treatment).
Alleria Windrunner promised her people that she would return one day, and return she did at the head of an Alliance strike force sent to seize the Sunwell in an attempt to compel the Blood Elves to surrender. While the attempt failed, the Alliance invasion of the Ghostlands that served as a distraction has gotten bogged down, with control of the zone switching between both sides. For the Horde, protecting Silvermoon is an absolute priority due to it's location as their last major presence in the Eastern Kingdoms and the presence of the large Blood Elven civilian population. For the Alliance, control of the Ghostlands would allow them to threaten the Horde's last capital in the Eastern Kingdoms and it ties up Horde resources.
Warfront Westfall: The breadbasket of the Kingdom of Stormwind and a soft target on the Alliance's western flank, Westfall is an obvious location for the Horde to strike in an attempt to gain a foothold in the southern Eastern Kingdoms and threaten the Alliance capital. Squads of Forsaken eagerly await permission to swarm the countryside, mowing down any human they can find and carrying their corpses back for resurrection as new Undead. The Alliance has a vested interest in protecting their people and preventing the Horde establishing a military presence this close to the heart of their kingdom.
So those are my guesses.
Anyone else have any?