I was on one of “those” websites, and a reputable WoW leaker had a since removed post up regarding a potential leak from Blizzard.
The story goes their Sub count has been leaked by accident (not a disgruntled employee or anything dramatic like that), including a very in-depth breakdown of the splits between accounts that only play Classic, only play Retail, and those that play both. Her source informed her, without mentioning specific numbers, that it painted quite a grim picture for Classic outside the initial 6-8 weeks.
From what she said, Blizzard are aware of the leak, and are seriously considering releasing the information themselves rather than it coming from an unknown source.
If the leak is true, what do you expect it to reveal?