I think it is likely that they slowed down partially due to market saturation, and partially to work on Rebellion, X-wing, Armada, and all the other Star Wars lines. If they pump it out too fast, too many people start picking and choosing.
I wish I had that kind of willpower, to pick and choose I mean. I haven't played my first session yet and with the arrival of "Special Modifications" this afternoon I just completed the collection so far. Man do I have a lot of reading to do.