I was able to get my Xbox One to finally get a Open NAT consistently by disabling the port forwards in my router set for the Xbox 360. My Current router does not support multiple consoles and figured I would give priority to the Xbox One.
I had setup the port forwards for my 360 on my router a long time ago and had forgotten about them. I was having issues the other night talking with while playing a multiplayer game. I was then looking for the NAT ports for the Xbox One. But now I have been able to confirm that all the Xbox One needs is UPnP enabled and no specific ports setup for the 360.
Now the detail NAT information says: Your network is behind a cone NAT.
Just thought I would share my findings in order to help others.