It's all based on where you live. If your expected delivery date is more then 18 months out; they won't show a date until it falls into the 18 month window.
Every market is getting a different date. From what I've seen, and own experience the shortest wait time appears to be the NY Metro market. I reserved mine couple weeks ago and received a dde of 11/08-01/09. And others have said the same, NY market there is only a 6 month or so wait.
Also probably effecting it is the fact that there are at least 6 dealers in the NY metro market. If they allocate a certain amount of cars per a dealer, that makes more cars available to the area.
Hope that helps.