Yes maybe so, but if the rumours are true about MS going full Cloud streaming for there base model which will offer as much power as there top tier console, Xbox can release there premium console with what ever they want in it which we all expect it to be expensive.
As for Nintendo, they already went Nvidia and Sony well, AMD works for them but I much rather prefer Nvidia over AMD and I am one customer happy to pay the difference.
You're going to be very disappointed if you really try to put any weight behind an NVIDIA mixed console for next gen. It isn't happening. Like Sony, they'll continue with AMD and have custom parts created for the chassis.