I think AMD has a big window of opportunity here. Due to NVIDIA opting to save money and go with the vastly cheaper Samsung 8nm process (see the EEE Times article summer of 2019 citing costs as the driving factor NVIDIA switched to Samsung) -
NVIDIA only saw a 10-15% gain in frames/watt despite a full node jump.
AMD has been delivering and exceeding its stated efficiency goals since they started talking about them in 2016. They have exceeded every energy efficiency claim since Ryzen 1 and they did that with RDNA 1(they guided the public to a 50% increase in energy efficiency).
Now again AMD is stating they will see a 50% jump in energy efficiency in RDNA 2. Now a 50% jump in energy efficiency
doesn't mean half the energy used. It is more like a jump from 10 frames/watt to 15 frames/watt. So an RDNA 2 card would use 2/3 (0.67) the power of an RDNA 1 card.
5700 XT draws 210 watts on average compared to 322 watts for the 3080 FE which is just about twice as fast. Keep in mind Navi 10 is 251mm^2 while 3080 is a 628mm^2 chip. So we have a ton of die size to work with also.
RDNA 2 could crank the wattage to the exact same as 3080, and performance if it scales well would be ... 210 watts x 2 (to reach 3080) x 0.67 (50% expected efficiency increase for RDNA 2) and you get.... 281 watts average gaming power consumption.
So AMD could equal 3080 performance for 40 less watts.... Yes AMD has not been at the ultra high end for a few gens.. but they DO have a window of opportunity here if they do decide to release the full 80 CU "big" Navi to gamers. They could even fall short of their stated 50% efficiency game and still be just about the exact same as NVIDIA.
Of course, this isn't all GPU magic. AMD is simply using a superior process in TSMC 7nm versus Samsung's revised 10nm node (8nm). But if RDNA 2 can improve that much over RDNA on what is essentially a slightly more mature node then hats off to AMD! I can't wait to see who is going to get my $400-$500 this fall to replace my 1070 Ti