I don't believe we will see Vega Nano based on Vega 56 or 64. Because of thermals makers need to go with TDP below 200W. It would require lower clocks and therefore be too close to old Fury X/R9 Nano performance level. It would be storm towards RTG if they release Vega nano only ~20% quicker compare to almost 3 years old products.
RTG tried to put chain on Fury/R9Nano leg by prohibitting HBM overclock in drivers early this year but it seems it is still not enough.
I am sad to say we have to wait for Vega refresh or Navi (again waiting... and meanwhile they should re-enable HBM overclock)
I disagree. A VEGA 56 with properly tuned voltage will lose no performance while hitting the 200W target.
GamerNexus graph:
Unfortunately, GamerNexus did not investigate how much lower power consumption you can hit with unaffected power limit + undervolt. Since they are trying to extract performance, they increase power limit in addition to the undervolt. From this data and many user reports of undervolt and power limiting, we can expect to extract the same amount of performance compared to stock, while hitting around 180-200W.
I personally tuned a VEGA 64 and got a nice undervolt of -150mV, from stock chip power of 220W to 185W while losing no performance. There was a slight increase in performance but it was within margin of error.