I think there are two possible explanations:
1. Marco's pessimistic take that they are clearing through existing inventory in slightly reconfigured and cheaper machines.
2. grecy's comment here that they needed to keep people hooked while they get the real bump out the door.
If the answer is 2, then they really can't wait too long. A few people will be satisfied that they can get 12 cores for $3800, but it's only a stop gap.
My pessimistic gut says Marco is right (see FCPx/exFCP fiasco), but I keep hoping he's wrong. Right now I have too much invested in PCIe in my studio (audio hardware) and might get one of these new 12 core boxes and nurse it along for as long as I can.
Geof