The biggest benefit of moving from the 16nm ASIC Bitmain Antminer S9 to a 7nm ASIC Bitcoin Miner is the potential benefit from the 60% better efficiency. Starting from the S9’s .1 j/GH that puts a 7nm Bitcoin Miner at .04j/GH. Not to mention the >50% size reduction meaning less silicon for potentially less cost.
“In comparison to 16FF+, TSMC 7nm is said to offer a 3.3x density, 30% speed, and a 60% power improvement.”
https://www.semiwiki.com/forum/content/6662-tsmc-talks-about-22nm-12nm-7nm-euv-e.html