On Blizzcon 2005, Chris Metzen said there are plans for 7 new planets throughout the lifespan of World of Warcraft. These planets will be accessible via the portals in Outland.
These were the portals created by Ner’Zhul in Warcraft 2: Beyond the Dark Portal.
There is a novelization of the RTS game written by Aaron Rosenberg to be on sale by May 2008 titled:
WORLD OF WARCRAFT: BEYOND THE DARK PORTAL
The novel will probably – and this is a guess, not a fact – reveal what happened with Turalyon and Alleria before Draenor was torn apart by the forces unleashed by the unstable portals of Ner’zhul.
So far there are 3 portals in-game: Death’s Door (Blade’s Edge), Portal Clearing (Zangarmarsh) and Twilight Ridge (Nagrand). Other four portals will be added to Outland in the future. Turalyon and Alleria probably ended up in one of those 7 planets.
- Read the map campaign missions of Warcraft 2: Beyond the Dark Portal.