Pondering for you all. What if the Nano is filling in the 380X segment? AMD has held off on the 380X. Think about it, why list Nano as 290X when you have 390X out? It wouldn't be a stretch to probably get a Nano running at 390X performance. However, if it was, it would directly compete with the 390s and potentially hurt sales of one or the other..
I'm guessing 380X performance might be closer to 290X. So if you've got Nano coming in around the same spot, releasing the 380X early could potentially cause a problem. Got two products competing against each other. Perhaps AMD wants a premium for Nano due to HBM but if 380X is out and offers the same performance for much less price, it would cut into Nano sales. Granted Nano will have a value for small form factor machines, but it might be harder for AMD to justify spending a premium on Nano when you can get a 380X that does the same for less price. Thus, Nano releases first for a bit, then the 380X comes later.