Why not? This is marketing 101. The product isn't set to release until September. Holding things back in order to dribble them out over the next few months helps keep the hype going. Unveiling everything now means the hype dies down before the product releases, whereas doing it this way lets them build up the hype over time to lead up to the release.
They aren't trying to conceal things from you in order to fool you into pre-ordering. If anything, the main issue is that they told us about 2.0 at all this early, but that decision was basically forced on them by the decision to include 2.0 content in Wave XIV (which was the correct decision, IMO).
If you feel you need to know what's in the package before buying, then don't pre-order and wait to buy until you know what's in the package. There's nothing wrong with doing that. (For the record, I've never pre-ordered any X-Wing products, myself, though it's mostly because I'm still catching up on previous waves...)

