During the "World of Warcraft: What's Next" panel at BlizzCon 2013, Blizzard's Chris Metzen walked the crowd through how players get from present day to way back when.
At the end of the current World of Warcraft storyline, former Horde Warchief Garrosh Hellscream is taken away in chains, to be put on trial. That trick never works. He escapes trial and meets up with a new friend with the ability to bend time.
Garrosh travels back to when the world made sense of him, his intent is to redeem the Orcish ideal. He wants the Orcs to be proud conquerors again. His most critical mission is to stop the moment when the Orcs of old drank demon blood and fall under the sway of The Burning Legion. He will build an Iron Horde with the Chieftans of Old, empowered with the tech of the present. He will lead his Iron Horde through a time-spanning Dark Portal to conquer the present day.
Old Draenor was a much more savage place than the Outlands World of Warcraft players are familiar with.
The only real civilization is a number of famous Orc clans.
Frostwolf Clan of Frostfire Ridge — Chieftain is Durotan, the Father of Thrall. Thrall gets to see where he came from, hang with his family. Will Durotan join the Iron Horde?
Shadowmoon Clan of Shadowmoon Valley — Chieftain is Ner'zhul, the original Lich King.
Shattered Hand Clan of the Spires of Arak — Chieftain Kargath Bladefist. He has blades for fists. Go figure.
Blackrock Clan of Gorgrond — Chieftain Blackhand. The backbone of the Iron Horde. Blackhand is a jerk.
Warsong Clan of Nagrand — Chieftain Grommash Hellscream. Plays a major role in the story. Will his anger get the best of him? They're like Mongols, riding wolves through the plains. He and Garrosh might have words.
Bleeding Hollow Clan of the Tanaan Peninsula — Chieftain Kilrogg Deadeye. Lives in what will one day be Hellfire. Shamanistic, dark, tribal, bloody-minded clan. They gouge out their own eyes to see the future. Yay!
Entering Old Draenor
Players are sent on a suicide mission through the Dark Portal to stop the Iron Horde invasion. They're dropped right into the action, much like Mists of Panderia.
The Horde start in Frostfire Ridge, a frozen area with towering volcanoes. They'll get wrapped up in a conflict between two competing Orc clans, the Frostwolf and Thunderlord. They'll also battle Ogres to claim the Bladespire Fortress as the Horde's expansion base.
The Alliance begin in Shadowmoon Valley, changed (or unchanged) drastically from the way it looked in the Burning Crusade expansion. It's an area always bathed in darkness, filled with rolling, moonlit hills. It's the home of Karabor (eventually the Black Temple), the holy temple of the Draenei. The Alliance battle the Iron Horde to free the city to use as their base.
The Plot Thickens, Spills Over
From these first steps into old Draenor, players will embark on a quest that culminate in a battle with a big bad. During the panel Chris Metzen stressed that that big bad wasn't Garrosh. "He's the guy behind the guy." That battle will spill over into the next, unannounced expansion, the first of many Blizzard has lined up as World of Warcraft encroaches on ten years of operation.