Blizzard Entertainment, the creator of games like Warcraft and Diablo, announced today that its newest expansion pack for the insanely popular World of Warcraft online game would be available for a preliminary download.

This is another of the first large-scale releases of a high-profile game that will take advantage of digital distribution, which has become increasingly popular with platforms like Valve’s Steam game distribution software. Blizzard also released Starcraft 2, the newest iteration of its sci-fi real-time strategy game. Chris Metzen, one of the lead designers for Blizzard, made the announcement at Blizzcon 2010 in Anaheim, Calif. today.

World of Warcraft’s other expansion packs were incredibly successful, with its first expansion selling 2.4 million units in 24 hours and its most recent one — Wrath of the Lich King — selling 2.8 million units in the first day.

Now that gamers won’t need to go out and buy a physical copy, and that Blizzard’s subscriptions for World of Warcraft continue to grow, it’s practically a given that the online game creator will smash its previous records for game sales. World of Warcraft has so far gathered 12 million monthly subscribers at $15 a pop.

Blizzard is taking a bit of a different direction with its newest expansion by catering to newer and lower level players with new content. Traditionally, expansion packs for online games focus on new content for players that have already reached the end of the game.

World of Warcraft: Cataclysm remakes the game’s world after the rise of one of the game’s biggest enemies, a dragon aspect named Deathwing, has torn the world of Azeroth apart. Areas released in the original World of Warcraft game have been redesigned, and the leveling process has been revamped.

The Cataclysm expansion launches December 7, and will be available for preliminary download in the next couple of months. Gamers won’t be able to actually play the expansion yet, but will be able to as soon as Blizzard flips the switch to turn the servers on.