All you kids are high as a kite with the power estimations. Near XBox One? Way over X360/PS3? I would greatly adjust your expectations.
I think it's a big mistake to use the maximum performance of nVidia X1 used in devkits to be made as the baseline for the power of shipping NX. Going to Pascal from Maxwell doesn't necessarily mean the power will be increased from X1. All it means is that the NX is using more efficient and newer architecture.
In all likelihood, Nintendo will aim for $200 range for the NX. This will limit the size of the battery (~3000mAH would be best you'd expect), quality of the screen, the size of the heatsink/cooling, and most importantly, the size of the SOC. X1 is pretty damn big for ARM CPU due to 256 Maxwell GPU cores. It's not a cool and power sipping SOC by ARM standards. The X1 in the Shield set top box is putting out 10~20W during gaming. That's way past cell phone and tablet territory. That's more power hungry than Core i5 in Surface Pro 4 (15W).
Also is unavoidable fact that the thing is a portable first and foremost, and that will be the baseline for the power envelope for gameplay. Docked mode really doesn't matter unless Nintendo forces all the games to have two distinct performance and thus gameplay modes. That's extra work that devs will not want. All you'll get is resolution bump when docked most likely.
[bold prediction] I suspect that move to Pascal isn't to increase the power from X1's maxwell cores, but rather to improve the efficiency for battery savings. You can do more with less with a newer architecture. This IMO means you will see DECREASE in core count from X1 to whatever will be used in NX. I can see Nintendo commissioning nVidia to make them a SOC with only two Denver 2 CPU cores and 128 Pascal GPU cores. I can maybe see dual Denver 2 + single or dual A53 core for some background operations, but you will not see Hexacore ARM config like X2, and you certainly won't see 256+ Pascal GPU cores. I also expect the clockspeeds in mobile mode to significantly reduced from X1 and X2, as much as 50% reduction perhaps. [/bold prediction]
This will still be a GIGNATIC leap from 3DS and should bring Wii U like performance in a mobile package, and that IMO is a marvel in itself anyways. IMO, you will see nearly identical looking looking Zelda: Breath of Wind on NX and the Wii U.