If you're talking about bus power cards, that's limited to GP107.
We've seen the 1080 -> 1070 transition, 180W -> 150W. Another cut will result in around 125W or so, well above "bus only power".
That's why I said if it happened it would be a harvested part. Turn off 25% of the SMs and drop the clocks a little and there's no reason that GP106 couldn't run off of board power.
If they take long enough to launch it, they could even use GDDR5X memory for power savings. I'm sure there's some modules to be harvested there as well.