That's a huge mountain to climb.
AMD would have to update its delta color compression (which hasn't been updated since Tonga) to be on par with NVIDIA's 4th gen delta color compression used in Pascal. (assuming 8GB GDDR6, providing memory bandwidth of 448.0 Gb/s)
I know but why would amd release a slower card that consumes same power as Radeon7/Vega64. That part is what makes no sense. That is something that will be very hard to believe and it will be DOA.