It doesn't help that that topic isn't exactly properly named... though, it does have a huge load of replies...
Basically, there has been a whoooollleee ton of speculation on what it is, chadz has teased that some of us may or may not be right but won't say who, so nobody still knows what the hell it is.
Supposedly all will be made clear soon enough (perhaps around Strategus time, which leads people to believe it may have to do with Strategus)