Retailers tracking the date when their customers will start to hibernate with their PCs this winter can breathe a little easier -- the release date for World of Warcraft:  The Burning Crusade, the expansion for the most popular MMORPG (see ''World of Warcraft:'  The Worst of Times'), has been pushed back from late November until January 23rd.  Blizzard Entertainment announced the change on Tuesday, attributing the delay to the need for more time to beta-test the new release.  That gives retailers the holiday season to sell WoW players some real world products before the time demands and new content of the expansion make it difficult to get their attention.