Details of a World of Warcraft expansion pack, titled Wrath of the Lich King, have been found on the online database of the US Patent and Trademark Office.

The title has formerly been seen on the database of the Unterhaltungssoftware Selbstkontrolle (USK), the German software ratings board, fuelling many rumours of a Leipzip Games Con announcement. The listing then mysteriously disappeared only to then surface in the States.

The fact that the filing was found in the trademark database with a 1B filing basis has led many to believe that the expansion is as good as on its way. The 1B filing means that there is an "intent-to-use". The Patent Office’s regulations states that "An intent-to-use application must include a sworn statement that applicants have a bona fide intention to use the mark in commerce".

So, when will the official announcement be made? Most bets are on a BlizzCon 2007 conference, a move that itself has a pedigree. In 2005 Blizzard used BlizzCon to announce Burning Crusade.

BlizzCon 2007 starts tomorrow in Anaheim, California.