The format of how Blizzard tells its story will change in this expansion, too. Mists of Pandaria itself, the game that comes in the box, will be a full, contained story. The entire arc of Mists of Pandaria will be there when you install the game, before any content patches at all. The content patches will be treated as sequels to that story. We will arrive on Pandaria when we install the game, have our adventures, and then see that story end. When the first patch hits, we will see Pandaria begin to be truly ravaged by our war.
While the steps taking us there are still unknown, Metzen did reveal that the war waged in those patches will reach a massive conclusion: We will lay siege to Orgrimmar to remove the mantle of warchief from Garrosh Hellscream's shoulders. It didn't sound as if it would be an Alliance-only venture, so it seems the new Warchief of the Horde will get a little too Old School Grom for their taste. However, there is a possibility that the Horde will get to deal a similar blow of their own ... Knowing the fate of Garrosh Hellscream, it's possible nobody is safe this expansion.