Apparently they've already been using the new file system for Heroes of the Storm. Now being introduced to World of Warcraft.
http://us.battle.net/wow/en/blog/136454 ... s-4-3-2014
Introducing Our New File Format: CASC
For nearly 20 years, Blizzard games have used a file format called Mo’PaQ (MPQ for short) as a way to compress and store game files. We’ve been able to introduce some great new technology using MPQ, such as our streaming client, but we’ve really pushed the file format far beyond what it was ever intended to be used for. Today, it’s become the source of a number of technical limitations for World of Warcraft.
To address these limitation and help us develop new technologies that will improve everyone’s game experience for years to come, we’re introducing a new proprietary file format that we call CASC (Content Addressable Storage Container). We’ll be using this new format in the Warlords of Draenor alpha and beta tests, and our intent is to convert everyone to the new format in a pre-expansion patch.
As geeky as it may sound, we’re extremely excited to be moving to this new file format. It provides a ton of benefits not only for us and our ability to support and patch the game, but also for players. Here are just a few of the benefits of the new CASC file format:
File Corruption—File repair tools are a thing of the past. The file structure maintains itself, helping to prevent errors during installation.
Speed—Real-world game performance should increase for many players thanks to a non-redundant file structure—in layman’s terms, the game can find the assets it’s looking for more quickly.
Patching—Updating your game files should be faster and more reliable. Patch data is integrated seamlessly, and no longer requires double the installation size on-disk when patching.
Client Hotfixing—CASC allows us to be able to hotfix client game data, similar to server hotfixes, giving us the ability to address client-side issues that would normally require a patch.
Streaming—The new format provides better support for streaming data and gives us greater flexibility to define how content updates are delivered and released.
Expandable—The file structure is built to allow easy integration of new technologies in the future that we haven’t even thought up yet.
. . . and more!
We’re already using this file format for Heroes of the Storm’s Technical Alpha test, and we’re looking forward to reaping its benefits for WoW. As we mentioned, the first big step in transitioning all WoW players over will be converting everyone’s World of Warcraft installs to the new file format prior to the expansion. Our goal is to make sure that’s as seamless and painless a changeover as possible, using as much of the existing installed data as possible to reduce additional downloads. We’ll have more info on the file conversion process as we get closer to the launch of Warlords of Draenor.