As far as no movement on the wave four front...
When the Transport and Tantive IV we announced, it was made very clear that this was not wave four and that would be released independently. For what it is worth, I think that indicates they do have a wave four lurking about somewhere.
I'm going to suggest that keeping waves 1 - 3 in stock has received focus, as there was a lot of complaining about not being able to get the existing ships, especially the earlier ones. We seen several shipments from China, and they have all been re-stocks of the earlier ships. Now that they are finally catching up with demand (at least for now), maybe we'll see some movement on new stuff. I think the pre-orders for the epic ships showing might be a sign that they're getting back to new stuff.