I quoted that statement because it was the most recent one I could find that have both Beta 3 and Open Beta referenced in them and a tenative date. Also if you read the post there is another 2 months in that calender before the release of the game (sound familiar?). The reason I'm bringing up this issue is because many gamers don't like to commit money to a game that little has been released about as well as a game in such a state of flux.
It's true many people will be using the open beta as a demo, and while I'd be lying if I said that I wasn't going to try out the game in such a sense between identifying bugs and tweaks myself. I think it would be beneficial (I quoted Supreme Commander because I believe they did such an extrodanarily good job in this area) for the game if it were to have an open beta at a good stage before release.
All this is besides the point though, all I really want to know is a rough official approximation, if not an exact date to when the open beta will be released, assuming one is indeed comming.