Blizzard has joined in on the recent trademarking party, filing three new trademarks for the name Cataclysm. The trademarks could apply to any number of unannounced projects, including a possible World of WarCraft expansion.
As reported by BlizzPlanet, the new project potentially relates to the Sundering, an event that occurred 10,000 years before World of WarCraft. The name refers to the implosion of the Well of Eternity, which was destroyed when the Burning Legion attempted to enter Azeroth.

At the moment, Blizzard is working on two unannounced projects -- a "next-generation massively multiplayer game," and what is speculated to be a new IP.

As Blizzard explained when describing their fifth project, "This brand-new game is not a World of Warcraft expansion, and it is not related to the next-gen MMO."

So could it be Cataclysm?

If there's anything to this trademark, there's a decent chance we'll be hearing about it at BlizzCon. But then, Blizzard has known to play their cards close to the chest in the past -- they didn't announce StarCraft II until it had been in development for four years.

For now, keep these new trademarks in mind ahead of any major announcements.