Internal timelines sometimes change, so if we were to reveal them and say that an update was supposed to come at a certain date and then we delay or change our schedule entirely to accomodate for a major issue or event like CS5 is released or we have a great new extension idea.... then we have users complaining that they made the decision and lost because the date wasn't accurate.
We just can't give out dates and predictions about the future that might be wrong because people like you would depend on them. It could hurt both sales and customer satisfaction if those dates weren't accurate, and may hurt sales by exposing them at all even if they were.