While it may very well be cancelled, I do want to note a couple of other points:
1) Vega is clearly supply constrained. The fact that there are no open air cards from partners points to this- they're only getting the supply now to do that, and Nano would be a lower priority.
2) There have been plenty of people successfully undervolting Vega cards and losing only minimal, if any, performance. I don't know what the TDPs are after undervolting, but you could potentially get something more reasonable if you binned chips for ones that undervolt well.