GM butchered it for 2007. It is gone for 2014. 2015 order guide shows no sign of an HD version.
Now there may be some hope. 2014 half ton pickups lost about 300 pounds keeping GVWR, so net payload is up. I half expect GM to do something similar for 2015 SUVs, but have not confirmed yet. And I have no idea if the receiver has the same problems as the 2007-2014 SUVs.
So: milk your 8.1L as long as you can!
Edit: Some quick research on the 2015. Lost 100 pounds. Curb weight of 4WD Yukon Denali is just under 6k pounds with 7500 pound GVWR. Tow rating max is 8000 pounds for 4WD. Does not look promising.