From experience of the game and all the quests I have found in Wrath of the Lich King and what I have read in the RPG books, there are two strong candidates for the next expansion:
- Emerald Dream
- South Seas
- Another world
The Emerald Dream was visited after doing the Argent Dawn quest in Icecrown: A Story of Valor. A very small portion of the Nightmare to be exact. We know Cenarius and Malfurion are fighting it. And that Ysera is being affected somehow as mentioned by Itharius at the Wyrmrest Temple. The phase technology introduced in Wrath of the Lich King is a very high indication that Blizzard is experimenting with it in preparation for the Emerald Dream. They could rehash the old world applying phased zones to each region. Blizzard has been working on the Emerald Dream for years. Back on 2003, before WoW launched, Tigole acknowledged the Emerald Dream was in development. Many are aware some of the Emerald Dream files were in their hard drives for quiet a long time, until they were removed during a patch.
The South Seas got a lot of lore in the World of Warcraft RPG: Lands of Mystery book (2006). I remind you all the lore of Northrend was revealed in that very same book a year before WoTLK was announced officially. The PDF downloadable version is still on sale at a lowered price. White Wolf Publishing authors mentioned each region of Northrend (Zul'Drak, Borean Tundra, Sholazar Basin, etc.) and the species of each region, dungeons and some plots in that RPG book. Basically, Blizzard gave them some of their game design notes to work on. South Seas is a perfect candidate for the next expansion for this matter -- because extensive info about it was bundled within the same book. The South Seas contain the Tomb of Sargeras (Broken Isles), Isle of Kezan (Undermine), Plunder Isle, Zandalar Isle, Tel Abim Isle, Nazjatar and the Eye of the Maelstrom. Who doesn't love Pirates and ships, matey?
Each WoW game and expansion has had a specific special boss as final boss: WoW Classic (Onyxia), Burning Crusade (Illidan), WoTLK (Arthas the Lich King). There is no doubt who the South Seas final boss is ... Queen Azshara.
There was a quest in Dragonblight, at the Tuskarr village, that hints doom is coming from the Sea. Sounds like there's something from the depths coming out. Whether that's the naga or one of the Old gods that's yet to be seen.
As for other worlds, Metzen mentioned three planets that had been already planned -- he mentioned this at Blizzcon 2005. And four more planets after those. These will be accessible through the portals of Outland. The three portals to what Metzen referenced are already in the game: Death's Door (Blade's Edge), Twilight Ridge (Nagrand), The Clearing (Zangarmarsh). These portals in Outland were what tore apart planet Draenor, after Ner'zhul used the Book of Medivh, the Skull of Gul'dan, the Scepter of Sargeras and the Eye of Dalaran to open new portals to other worlds in order to conquer them. This was the main topic of Warcraft 2: Beyond the Dark Portal and what inspired the development of the Burning Crusade expansion. You can read how the events unfolded in the pocket star book ... World of Warcraft: Beyond the Dark Portal by Aaron Rosenberg & Christie Golden.
Mal'ganis said he would return to the homeworld to recover his strength ... so we got a perfect square-in-the-jaw hint the homeworld of the dreadlords still exists ... Xoroth.
There is also the possibility that we get a mix of two of these candidates. After all Burning Crusade introduced not only Outland, but two new areas: Quel'Thalas and Azuremyst. If you are a lore guru, share your own predictions.







Good conjecture, but I’d like to pick on one little nit (more a question really). Isn’t this southseas you mention essentially the Maelstrom expansion as people have been calling it?