My guess is if the Nvidia rumors are true, then Nintendo is maybe using a custom Tegra X1. It's a good mobile chip, the tech behind is reasonably tested as Nvidia's had the Tegra X1 in the Shield micro-console for over a year now already.
Maybe the Nintendo console will be a custom 1 TFLOP (2x the current Tegra X1) Nvidia chip @ 20 watts, the portable may be 1/2 to 1/4 that.
This would line up with not being quite as good as an XBox One but still "industry leading" ... for a *mobile* chip, the Tegra X1 is pretty high end.
This is based on *if* what Emily and Semi-Accurate are saying is legit.