True, but there's what, one only company capable of making mobile GPUs poweful enough? By the way, that's the kind of low end chip that can go in a handheld/hybrid console like the Switch successor.
And yes, Tegra when it comes to the mobile market has been a failure, but Nvidia has found another market for it with self driving vehicles and AI. Not ideal for a console, mind you, as they focus on computing and the CPU side of it, but it's a template that they can use to make a design that works for Nintendo.
Maybe... but I'd far rather see Nintendo be a cutting edge ARM Mali customer than some using left over bits of Nvidia's afterthoughts. Maybe they can magic up a custom Nvidia laptop chip that does Tegra backwards compatibility?